Preparation And Isolation of 5&#39; Capped mRNA

ABSTRACT

The synthesis of capped/tagged RNA, methods of use and kits providing same are contemplated. Tagged RNA permits isolation of RNA transcripts in vitro. The ability to isolate and purify capped RNA results in improved transcription and translation and provides a tool for identifying RNA-protein interactions. Such capped RNA finds use in therapeutic applications, diagnosis and prognosis and in the treatment of cancers and HIV.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of International Application No.PCT/US08/081,651, filed on Oct. 29, 2008, which application claims thebenefit of U.S. Provisional Application No. 60/984,320, filed on Oct.31, 2007. Said applications are incorporated herein by reference intheir entirety.

The section headings used herein are for organizational purposes onlyand should not be construed as limiting the subject matter describedherein in any way.

INTRODUCTION

Eukaryotic mRNAs bear a “cap” structure at their 5′-termini that is wellknown to play an important role in translation. Naturally occurring capstructures comprise a 7-methyl guanosine that is linked via atriphosphate bridge to the 5′-end of the first transcribed nucleotide,resulting in m⁷G(5′)ppp(5′)N, where N is any nucleoside (Nuc). The mRNAcap plays an important role in gene expression. It protects the mRNAsfrom degradation by exonucleases, enables transport of RNAs from thenucleus to the cytoplasm and participates in assembly of the translationinitiation complex. m⁷G(5′)ppp(5′)G (mCAP) has been used as thedinucleotide cap in transcription with T7 or SP6 RNA polymerase in vitroto obtain RNAs having a cap structure in their 5′-termini. In vivo, thecap is added enzymatically. However, over the past 20 years or so,numerous studies have required the synthesis of proteins in an in vitrotranslation extract supplemented with in vitro synthesized mRNA. Theprevailing method for the in vitro synthesis of capped mRNA employs apre-formed dinucleotide of the form m⁷G(5′)ppp(5′)G (m⁷GpppG) as aninitiator of transcription. A disadvantage of using mCAP, apseudosymmetrical dinucleotide, has always been the propensity of the3′-OH of either the G or m⁷G (m⁷Guo) moiety to serve as the initiatingnucleophile for transcriptional elongation. This leads to the synthesisof two isomeric RNAs of the form m⁷G(5′)pppG(pN)_(n) andG(5′)pppm⁷G(pN)_(n), in approximately equal proportions, depending uponthe ionic conditions of the transcription reaction. This may beproblematic for various downstream processes, such as in vitrotranslation or crystallization studies.

To date, the usual form of a synthetic dinucleotide cap used in in vitrotranslation experiments is the ARCA. The Anti-Reverse Cap Analog (ARCA)is most often a modified cap analog in which the 3′ OH group is replacedwith OCH₃. ARCA and triple-methylated cap analogs are incorporated inthe forward orientation. The selective procedure for methylation ofguanosine at N7 and 3′ O-methylation and 5′ diphosphate synthesis hasbeen established (Kore, A. and Parmar, G. Nucleosides, Nucleotides, andNucleic Acids, 25:337-340, (2006) and Kore, A. R., et al. Nucleosides,Nucleotides, and Nucleic Acids 25(3): 307-14, (2006).

In the cell, the cap is added in the nucleus and is catalyzed by theenzyme guanylyl transferase. The addition of the cap to the 5′ terminalend of RNA occurs after initiation of transcription but immediatelyafter transcription initiation so that it is almost impossible todetect. The terminal nucleoside is always a guanosine, and is in thereverse orientation to all the other nucleotides, i.e.,G(5′)ppp(5′)GpNpNp . . . and the cap contains two nucleotides, connectedby a 5′-5′ triphosphate linkage.

Transcription of RNA usually starts with a nucleoside triphosphate(usually a purine, A or G). When transcription occurs in vitro, ittypically comprises a phage RNA polymerase such as T7, T3 or SP6, a DNAtemplate containing a phage polymerase promoter, nucleotides (ATP, GTP,CTP and UTP) and a buffer containing magnesium salt. The synthesis ofcapped RNA includes the incorporation of a cap analog (e.g., N7 methylGpppG or m⁷GpppG) in the transcription reaction. Excess m⁷GpppG to GTP(4:1) favors to increase the opportunity that each transcript will havea 5′ cap. The mMESSAGE mMACHINE® kit from Ambion (Ambion, Inc., Austin,Tex., a business of Applied Biosystems) recommends this ratio and willtypically yield 80% capped RNA to 20% uncapped RNA, although total RNAyields are lower as GTP concentration becomes rate limiting as GTP isneeded for the elongation of the transcript. However, the transcriptionreaction products contain unincorporated NTPs, enzymes and buffercomponents as well as uncapped RNA transcripts which interfere withtranslation efficiency and protein yield.

The recent literature reveals that chemical modification of m7Guo ateither the 2′ or 3′ OH group of the ribose ring results in the cap beingincorporated solely in the forward orientation, even though the 2′ OHgroup does not participate in the phosphodiester bond. However,currently there is no technology/method available, which will allowresearchers and developers of RNA therapeutics to selectively isolateonly capped RNA from uncapped fragments. In order to overcome thisbarrier, disclosed herewith are novel cap analogs which have beendesigned and synthesized with reporter moieties allowing purificationand isolation of only the capped RNA transcript. Clearly, the art is inneed of a novel method of synthesizing dinucleotide cap analogs with areporter moiety and isolation protocols. The creative use of affinitytags as the reporter moiety will provide a simple and skillful means toisolate and purify capped RNA transcripts from the transcriptionreaction mixture.

The discovery of a method of synthesizing dinucleotide cap analogs witha reporter moiety attached, the attachment of a reporter moiety to adinucleotide cap post-transcription, and the subsequent retrieval andpurification of the capped RNA transcript is disclosed herein.Experiments in which the reporter moiety-labeled RNA transcript wasisolated from the transcription reaction followed by cleavage of thereporter moiety from the tagged RNA to yield purified capped RNAtranscripts show that the capped RNA transcripts are successfullytransfected and have demonstrated improved translation efficiency andprotein yields when compared to RNA caps without a reporter moietyattached.

The structure of the novel cap analogs were confirmed by ¹H NMR, ³¹PNMR, and mass spectroscopy. Methods to isolate and purify capped RNAtranscripts were developed using biotin as the affinity tag. Standard invitro transcription reactions were performed by using pTri β actinvector in the presence of T7 RNA polymerase and the novel cap analogs.Capping assays indicate that these new caps are substrates for T7 RNApolymerase.

Because the 5′ cap structure enhances the translation of mRNA by helpingto bind the eukaryotic ribosome and assuring recognition of the properAUG initiator codon, providing purified capped RNA assists intranslation efficiency. Capped RNA encoding specific genes can betransfected into eukaryotic cells or microinjected into cells or embryosto study the effect of the translated product in the cell or embryo. Ifuncapped RNA is used, the RNA in these experiments is rapidly degradedand the yield of translated protein is substantially reduced. The cappedRNA transcript finds use in both in vivo and in vitro translationstudies. These results provide important improvements in therapeuticdelivery mechanism, vaccine production, diagnoses and RNA-proteininteraction studies as well as providing efficient use of often limitedRNA samples, thereby conserving and extending sample availability.

The synthesis of capped RNA efficiently to yield high levels oftranscribed RNA is an area of unmet need as is the need to isolate andpurify capped RNA molecules in vitro, ideally, capped RNAs with caps inthe proper orientation. Thus, there exists in the art a need for highyield transcription reactions that efficiently synthesize RNA. Theresulting RNA finds use in a variety of applications, includingribozyme, antisense and biophysical studies, and gene array analysis.Additionally, capped RNA transcripts are used for applications requiringprotein synthesis such as in vivo expression (e.g., microinjection,transfection and infection experiments) and in vitro translation. Thus,the instant application provides novel technological improvements havingimportant applications in universal labeling and detection,therapeutics, diagnostics, and vaccine development.

SUMMARY

In one aspect, provided herein is a dinucleotide cap analog useful forspecifically transcribing an mRNA molecule of interest. The dinucleotidecap analog composition comprises:

wherein: B is a nucleobase; R₁ is selected from a halogen, OH, and OCH₃;R₂ is selected from H, OH, and OCH₃; R₃ is CH₃ or void; R₄ is NH₂; R₅ isH; and n is 1, 2 or 3; wherein a linker is attached to one of R₁, R₂,R₄, R₅, or B and R₁ or R₂ is OH.

The nucleobase can be a nucleobase or nucleobase analog that isoperative in accordance with the various compositions and methodsdescribed herein. In some embodiments, the nucleobase can be a purine,purine analog, pyrimidine, pyrimidine analog and natural, synthetic andderivatives thereof. In some embodiments, the nucleobase can be adenine,adenine analogs and natural, synthetic and derivatives thereof. In someembodiments the nucleobase can be uracil, uracil analogs and natural,synthetic and derivatives thereof. In yet other embodiments, thenucleobase can be guanine, guanine analogs and natural, synthetic andderivatives thereof.

In some embodiments, the linker can be N, S, and O. In some embodiments,the linker can be an aminoallyl ([—CH₂]_(n)CH₂NH₂) where n=2-18, asecondary amine and an alkyl (C₃-C₁₀)NH₂ chain. In some embodiments thealkyl chain can comprise three to ten chain atoms with a terminalprimary amine. In some embodiments the linker can be a cleavable or canbe a non-cleavable linker. In such embodiments, the linker can beattached by a first end to the nucleobase and can have a second end witha reactive group which can be available for binding to a reportermoiety. In some embodiments, the linker can be covalently linked to thenucleobase. In some embodiments, if the nucleobase comprises a purinebase, the linker can be attached to the 2-position (R₄) or 8-position(R₅) of the purine, if the nucleobase comprises a 7-deazapurine base,the linker moiety can be attached to the 7-position of the7-deazapurine, and if the nucleobase comprises a pyrimidine base, thelinker moiety can be attached to the 5-position of the pyrimidine. Insome embodiments the linker moiety can be attached to the 2′ or 3′position of the ribose ring attached to the methylated 7-position of theguanine.

The reporter moiety can be attached to the linker at the linker'sreactive group. The reporter moiety can be any moiety capable of bindingto a substrate, for example, a magnetic bead, a chromatography columnbound with, for example, avidin, streptavidin, antigen, antibody, andthe like. In some embodiments, the reporter moiety can be an affinitytag or an epitope tag. In further embodiments, the affinity tag can beselected from biotin, iminobiotin, avidin, and streptavidin.Non-limiting examples of biotin molecules that can comprise the reportermoiety include C₅-C₂₀-biotin, SS-biotin, XX-biotin, and NHS estercompounds thereof.

In another aspect, the dinucleotide cap analog is useful in thetranscription of DNA to mRNA and the subsequent purification of thetranscribed mRNA. In some embodiments the dinucleotide cap analog isattached to the 5′ end of an RNA molecule. In such embodiments, the capanalog can facilitate the isolation and purification of capped,transcribed RNA from a transcription reaction mixture.

Also provided is a method of synthesizing a detectable dinucleotide capanalog comprising: a) providing a guanosine nucleoside optionallycomprising either a 2′ substituent or a 3′ substituent and optionallycomprising a linker; b) phosphorylating the first nucleoside, forming afirst nucleotide; c) methylating the first nucleotide; d) adding aphosphorylated second nucleotide optionally comprising a linker; e)coupling said first nucleotide with said second nucleotide, forming adinucleotide cap analog. In one embodiment a reporter moiety can beattached to said linker. In some embodiments the first nucleotide can beguanosine, which can be methylated at the N7 position. In variousembodiments the 2′ substituent of said first nucleotide can be ahalogen, OH or OCH₃ and the 3′ substituent of said first nucleotide canbe OH or OCH₃. In some embodiments one of the 2′ or 3′ substituents isOH. In some embodiments the halogen can be fluorine. In some embodimentsthe coupling of the first and second nucleotides can be catalyzed byZnCl₂.

Also provided is a method for isolating a dinucleotide capped moleculecomprising: a) providing a nucleic acid mixture containing adinucleotide cap analog attached to the 5′ end of an RNA molecule. Insome embodiments, the 5′ capped RNA molecule is present in a purifiedform. In some embodiments, the capped RNA can be isolated by use of areporter moiety attached to a linker attached to the RNA cap analog; b)binding the reporter moiety of step a) to a substrate; c) extracting thecomplex of step b) from the nucleic acid mixture; and optionally, d)removing the reporter moiety from the capped nucleic acid; whereincapped nucleic acids are isolated.

Also provided is a composition comprising: an antigen presenting celltransfected with a capped nucleic acid obtained by a) providing anucleic acid mixture containing a dinucleotide cap analog attached tothe 5′ end of an RNA molecule. In some embodiments, the 5′ capped RNAmolecule is present in a purified form. In some embodiments, the cappedRNA can be isolated by use of a reporter moiety attached to a linkerattached to the RNA cap analog; b) binding the reporter moiety of stepa) to a substrate; c) extracting the complex of step b) from the nucleicacid mixture; and d) removing the linker from the capped nucleic acid;wherein capped nucleic acids are isolated.

Also provide is a composition comprising an antigen presenting celltransfected with a dinucleotide cap analog attached to the 5′ end of anRNA molecule. In some embodiments, the 5′ capped RNA molecule is presentin a purified form. In some embodiments, the capped RNA can be isolatedby use of a reporter moiety attached to a linker attached to the RNA capanalog. The reporter moiety can be any moiety capable of binding to asubstrate, for example, a magnetic bead, a chromatography column boundwith, for example, avidin, streptavidin, antigen, antibody, and thelike. Such a reporter moiety can be an affinity tag or an epitope tag.In some embodiments, the affinity tag can be selected from biotin,iminobiotin, avidin, and streptavidin. Non-limiting examples of biotinmolecules that can comprise the reporter moiety include C₅-C₂₀-biotin,SS-biotin, XX-biotin, and NHS ester compounds thereof.

Also provide is a dinucleotide cap analog within a cell. In someembodiments the first nucleotide of the cap can be guanosine, which canbe methylated at the N7 position. In some embodiments the nucleobase ofthe second nucleotide can be a purine or a pyrimidine as well asnatural, synthetic and derivative nucleobases thereof. In variousembodiments the 2′ substituent of said first nucleotide can be ahalogen, OH or OCH₃ and the 3′ substituent of said first nucleotide canbe H, OH or OCH₃. In some embodiments one of the 2′ or 3′ substituentsis OH. In some embodiments the halogen can be fluorine. In someembodiments the dinucleotide cap analog is attached to the 5′ end of anRNA molecule. In some embodiments, the 5′ capped RNA molecule is presentin a purified form. In some embodiments, the capped RNA can be isolatedby use of a reporter moiety attached to a linker attached to the RNA capanalog. The reporter moiety can be any moiety capable of binding to asubstrate, for example, a magnetic bead, a chromatography column boundwith, for example, avidin, streptavidin, antigen, antibody, and thelike. Such reporter moiety can be an affinity tag or an epitope tag. Insome embodiments, the affinity tag can be selected from biotin,iminobiotin, avidin, and streptavidin. Non-limiting examples of biotinmolecules that can comprise the reporter moiety include C₅-C₂₀-biotin,SS-biotin, XX-biotin, and NHS ester compounds thereof.

Generally, the present teachings include dinucleotide CAP analogcompounds having attached thereto a reporter moiety. Such detectabledinucleotide CAP analogs when attached to an RNA molecule are useful inidentification, quantification, and purification/isolation of cappedRNA, purification of transcribed RNA, in the expression of proteins,transfection of dendritic cells, synthesis of vaccines and proteinproduction within, for example, HeLa cells, identification ofRNA-protein interactions, for the identification of RNA, in the analysisof proteins, and in methods utilizing such CAP analogs and reagents inthe area of therapeutics, diagnostics and prognostics. The disclosedcompounds of the present teachings may find particular application inthe area of purification of capped RNA, RNA transfection into dendriticcells, vaccine development, therapeutics and diagnostics

Also provided are kits for performing methods of the present teachings.For example, in some embodiments the kits include a dinucleotide capanalog useful for specifically transcribing an mRNA molecule ofinterest. The dinucleotide cap analog composition comprises:

-   -   wherein: B is a nucleobase; R₁ is selected from a halogen, OH,        and OCH₃; R₂ is selected from H, OH, and OCH₃; R₃ is CH₃ or        void; R₄ is NH₂; R₅ is H; and n is 1, 2 or 3; wherein a linker        is attached to one of R₁, R₂, R₄, R₅, or B and an RNA        polymerase.

In various embodiments, the kits can include a reporter moiety, attachedto the linker found within the dinucleotide cap analog composition,useful for isolation and purification of transcribed mRNA. In someembodiments, the kits include nucleotides, ribonuclease inhibitor andDNase. In some embodiments, the kits include an enzyme such as an RNApolymerase, including but not limited to SP3, SP6 and T7 polymerases,and a buffer, such as enzyme or nucleotide buffers. In some embodimentsthe reporter moiety within the kits is selected from an affinity tag andan epitope tag. In some embodiments, the reporter moiety can be anaffinity tag such as biotin.

These and other features of the present teachings are set forth herein.

BRIEF DESCRIPTION OF THE FIGURES

The skilled artisan will understand that the drawings, described below,are for illustration purposes only. The drawings are not intended tolimit the scope of the present teachings in any way.

FIG. 1 provides the general structure of a biotin-labeled mCAP analog;

FIG. 2 provides examples of dinucleotide cap analogs with non-cleavablelinkers attached to the affinity tag biotin;

FIG. 3 provides the synthesis of m⁷G[5′]pppp[5′]U-18-biotin with anon-cleavable linker;

FIG. 4 provides the synthesis of m⁷G[5′]pppp[5′]U—S—S-biotin with acleavable linker;

FIG. 5 provides a scheme for the preparation of 5′ capped/biotin mRNApre-transcription;

FIG. 6 provides a scheme for attaching the biotin tag to the cap analogfollowing transcription and the subsequent isolation of 5′ capped mRNAtranscript;

FIG. 7 provides a scheme for the preparation of 5′ capped/biotin mRNAwith an ARCA cap analog, pre-transcription;

FIG. 8 provides a scheme for the preparation and isolation of 5′ cappedmRNA with an ARCA cap analog, post-translation;

FIG. 9 provides the results of a Gel Shift assay showing greater yieldsof transcribed RNA and so increased transcription efficiency when RNA iscapped vs. uncapped;

FIG. 10 provides a comparison of transcription yields of RNA capanalogs, analogs with and without linker or linker plus biotin tag;

FIG. 11 illustrates the RNA transcript yield obtained from atranscription reaction when using the capped RNA analogs of the presentinvention.

DESCRIPTION OF VARIOUS EMBODIMENTS

It is to be understood that both the foregoing general description andthe following description are exemplary and explanatory only and are notrestrictive of the compositions and methods described herein.

For the purposes of interpreting this specification, the followingdefinitions will apply and whenever appropriate, terms used in thesingular will also include the plural and vice versa. In the event thatany definition set forth below conflicts with the usage of that word inany other document, including any document incorporated herein byreference, the definition set forth below shall always control forpurposes of interpreting this specification and its associated claimsunless a contrary meaning is clearly intended (for example ininterpreting the document where the term is originally used). The use of“or” herein means “and/or” unless stated otherwise or where the use of“and/or” is clearly inappropriate. The use of “a” herein means “one ormore” unless stated otherwise or where the use of “one or more” isclearly inappropriate. The use of “comprise,” “comprises,” “comprising,”“include,” “includes,” and “including” are interchangeable and notintended to be limiting.

As used herein, the term “affinity tag” refers to a moiety that can beattached to a nucleotide or nucleotide analog, and that is specificallybound by a partner moiety. The interaction of the affinity tag and itspartner provides for the detection of molecules bearing the affinitytag. Examples include, but are not limited to biotin or iminobiotin andavidin or streptavidin. A sub-class of affinity tag is the “epitopetag,” which refers to a tag that is recognized and specifically bound byan antibody or an antigen-binding fragment thereof.

As used herein, the term “alkyl” refers to a saturated or unsaturated,straight-chain, branched, or cyclic hydrocarbon radical derived by theremoval of one hydrogen atom from a single carbon atom of a parentalkane, alkene, or alkyne. Typical alkyl groups include, but are notlimited to, methyl, ethyl, propyl, butyl, and the like. Typical alkylgroups include, but are not limited to, methyl (—CH₃); ethyls such asethanyl (—CH₂—CH₃), ethenyl (—CH≡CH₂), ethynyl (—C≡CH); propyls such aspropan-1-yl (—CH₂—CH₂—CH₃), propan-2-yl, cyclopropan-1-yl,prop-1-en-1-yl (—CH═CH—CH₂), prop-1-en-2-yl, prop-2-en-1-yl(—CH₂—CH═CH₂), prop-2-en-2-yl, cycloprop-1-en-1-yl; cycloprop-2-en-1-yl,prop-1-yn-1-yl (—C≡C—CH₃), prop-2-yn-1-yl (—CH₂—C≡CH), etc.; butyls suchas butan-1-yl (—CH₂—CH₂—CH₂—CH₃), butan-2-yl, cyclobutan-1-yl,but-1-en-1-yl (—CH═CH₂—CH₂—CH₃), but-1-en-2-yl, but-2-en-1-yl(—CH₂—CH═CH₂—CH₃), but-2-en-2-yl, buta-1,3-dien-1-yl (—CH═CH—CH═CH₂),buta-1,3-dien-2-yl, cyclobut-1-en-1-yl, cyclobut-1-en-3-yl,cyclobuta-1,3-dien-1-yl, but-1-yn-1-yl (—C≡C—CH₂—CH₃), but-1-yn-3-yl,but-3-yn-1-yl (—CH₂—CH₂—C≡CH), etc.; and the like.

As used herein, the term “aminoallyl” refers to a carbon atom chain ofthe formula ([—CH₂]_(n)CH₂NH₂) where n=2-18. The aminoallyl group ismost often found attached to the 5-position of the pyrimidine ring ofuracil and cytosine. When attached to a nucleotide, it can beabbreviated as “aa-UTP” or “aa-CTP”.

As used herein, the term “antigen presenting cell” (APC) refers to acell displaying an antigen-MHC complex on its surface. The T-cellreceptor of T-cells may recognize the antigen. Examples of APCs includewithout limitation dendritic cells, macrophages, B-cells, fibroblasts(skin), thymic epithelial cells, thyroid epithelial cells, glial cells(brain), pancreatic beta cells, and vascular endothelial cells.(Steinman, R. M. and J. Banchereau, Nature 449, 419-426 (2007))incorporated herein by reference).

As used herein, the term “cell” refers to any eukaryotic or prokaryoticcell cultured in vitro for therapeutic, diagnostic or research purposes.Cells can originate from embryos, tissues and diseased tissues,including but not limited to blood, liver, muscle, melanoma,glioblastoma, lymphoma, carcinoma, epithelium, neuroblastoma,glioblastoma, colorectal carcinoma/lung metastasis, ovarian, prostate,uterine, mammary, breast, hybridoma, kidney, prostrate, lung, heart,brain and skin. Cells can be derived and/or isolated from embryonic stemcells, B-cells, T-cells, bone marrow and so on.

As used herein, the term “ARCA” or Anti-Reverse Cap Analog refers to amodified cap analog in which the 2′ and/or 3′ OH group on the guanosineis replaced with—another chemical moiety. An example of an ARCAstructure representation is m₂ ^(7,3′/0)G(5′)ppp(5′)G Table 1 identifiesARCAs contemplated in the current application.

As used herein, the term “cap” refers to a non-extendible dinucleotidethat facilitates translation or localization, and/or preventsdegradation of an RNA transcript when incorporated at the 5′ end of anRNA transcript, typically having an m⁷GpppG or m⁷GpppA structure. Innature the modified base 7-methylguanosine is joined in the oppositeorientation, 5′ to 5′ rather than 5′ to 3′, to the rest of the moleculevia three phosphate groups i.e., P1-guanosine-5′-ylP3-7-methylguanosine-5′-yl triphosphate (m⁷G5′ ppp5′G). The cap mayinclude a triphosphate, a tetraphosphate or a pentaphosphate groupjoining the two nucleotides.

As used herein, the term “cap analog” refers to a structural derivativeof an RNA cap that may differ by as little as a single element.

As used herein, the term “mCAP” refers to a dinucleotide cap with the N7position of the guanosine having a methyl group. The structure can berepresented as m⁷G(5′)ppp(5′)G, though a triphosphate, a tetraphosphateor a pentaphosphate group can join the two nucleotides. mCAP can used asthe dinucleotide cap in transcription with T7, SP3 or SP6 RNA polymerasein vitro to obtain RNAs having a cap structure in their 5′-termini.

As used herein, the term “enzymatically incorporatable” means that anucleotide is capable of being enzymatically incorporated onto theterminus, e.g. 3′ terminus, of a polynucleotide chain, or internallythrough nick-translation of a polynucleotide chain, through action of atemplate-dependent or template-independent polymerase enzyme. Anucleotide-5′-triphosphate is an example of an enzymaticallyincorporatable nucleotide.

As used herein, the term “enzymatically extendable” or “3′ extendable”means a nucleotide or polynucleotide that is capable of being appendedto a nucleotide or polynucleotide by enzyme action. A polynucleotidecontaining a 3′ hydroxyl group is an example of an enzymaticallyextendable polynucleotide.

As used herein, the term “halogen” refers to nonmetal elements of Group7A of the Periodic Table of the Elements comprising fluorine (F),chlorine (Cl), bromine (Br), iodine (I), and astatine (At). Halogens aremonovalent, readily form negative ions and occur as compounds or ions.

As used herein, the term “linker” refers to the chemical group(s) whichjoins a reporter moiety, e.g., an affinity tag, to a dinucleotide capanalog. The nucleobase, a ribose or analogs thereof within thedinucleotide cap analog may be modified to contain a reactive group(e.g., an amine on an aminoallyl or alkynyl amine), with a reportermoiety attached. The “linker” according to the invention is consideredto be the chemical entity or entities between the dinucleotide cap andthe reporter moiety. That is, the “linker” encompasses any modifyinggroup added to the dinucleotide cap in order to provide conjugationbetween the dinucleotide containing linker w/primary amine and thereporter moiety having an NHS ester group for the attachment of areporter moiety. In various embodiments, useful linkers include, but arenot limited to N, S, and O, an aminoallyl ([—CH₂]_(n)CH₂NH₂) wheren=2-18, a secondary amine and an alkyl (C₃-C₁₀)NH₂ chain. Linkers caninclude, for example, an alkyl, allyl, or alkynyl amine modifying groupattached to the nucleobase. As an alternative, linkers can include oneor more ethylene oxy moieties.

As used herein, the term “nucleobase” refers to a nitrogen containingheterocyclic moiety nucleobase of a nucleotide or a nucleotide analog.Non-limiting examples of suitable nucleobases include: adenine,cytosine, guanine, thymine, uracil, 5-propynyl-uracil,2-thio-5-propynyl-uracil, 5-methylcytosine, pseudoisocytosine,2-thiouracil, 2-thiothymine, 2-aminopurine, N9-(2-amino-6-chloropurine),N9-(2,6-diaminopurine), hypoxanthine, N9-(7-deaza-guanine),N9-(7-deaza-8-aza-guanine) and N8-(8-aza-7-deazaadenine), includingnaturally-occurring and synthetic derivatives. Additional nucleobasesthat can be used in the practice of the disclosed embodiments includepyrazolo[3,4-d]pyrimidines, 5-methylcytosine, 5-hydroxymethy cytosine,xanthine, hypoxanthine, 2-aminoadenine, 6-methyl and other alkylderivatives of adenine and guanine, 2-thiouracil, 2-thiothymine and2-thiocytosine, 5-halouracil and cytosine, 5-propynyl uracil andcytosine, 6-azo uracil, cytosine and thymine, 5-uracil (pseudouracil),4-thiouracil, 8-halo, 8-amino, 8-thiol, 8-thioalkyl, 8-hydroxyl andother 8-substituted adenines and guanines, 5-halo particularly 5-bromo,5-trifluoromethyl and other 5-substituted uracils and cytosines,7-methylguanine and 7-methyladenine, 8-azaguanine and 8-azaadenine,7-deazaguanine and 7-deazaadenine and 3-deazaguanine, 3-deazaadenine,pyrazolo[3,4-d]pyrimidine, imidazo[1,5-a]1,3,5 triazinones, 9′deaapurines, imidazo[4,5]d]pyrazines, thiazolo[4,5-d]primidines,pyrazin-2-ones, 1,2,4]triazine, pyridazine; and 1,3,5 triazine and soon. Nucleobases useful in the various embodiments described permitattachment to and transcription of RNA molecules and furthermore, mayalso have attached to them a reporter moiety useful in the detection andpurification of the transcribed RNA. One of skill in the art wouldrecognize that modified forms and functional analog nucleobases are alsospecifically contemplated.

The term “nucleoside” and “nucleotide” refers to a compound having apyrimidine nucleobase, for example cytosine (C), uracil (U), or thymine(T), or a purine nucleobase, for example adenine (A) or guanine (G),linked to the C-1′ carbon of a “natural sugar” (i.e., -ribose,2′-deoxyribose, and the like) or sugar analogues thereof, including2′-deoxy and 2′-hydroxyl forms. Typically, when the nucleobase is C, Uor T, the pentose sugar is attached to the N¹-position of thenucleobase. When the nucleobase is A or G, the ribose sugar is attachedto the N⁹-position of the nucleobase (Kornberg and Baker, DNAReplication, 2^(nd) Ed., Freeman, San Francisco, Calif., (1992)). Theterm “nucleotide” as used herein refers to a phosphate ester of anucleoside as a monomer unit or within a polynucleotide, e.g.,triphosphate esters, wherein the most common site of esterification isthe hydroxyl group attached at the C-5′ position of the ribose.

“Nucleoside analog” and “nucleotide analog” refer to compounds havingmodified nucleobase moieties (e.g., pyrimidine nucleobase analogs andpurine nucleobase analogs described below), modified sugar moieties,and/or modified phosphate ester moieties (e.g., see Scheit, NucleosideAnalogs, John Wiley and Sons, (1980); F. Eckstein, Ed., Oligonucleotidesand Analogs, Chapters 8 and 9, IRL Press, (1991)). The ribose or riboseanalog may be substituted or unsubstituted. Substituted ribose sugarsinclude, but are not limited to, those riboses in which one or more ofthe carbon atoms, such as the 2′-carbon atom or the 3′-carbon atom, canbe substituted with one or more of the same or different substituentssuch as —R, —OR, —NRR or halogen (e.g., fluoro, chloro, bromo, or iodo),where each R group can be independently —H, C₁-C₆ alkyl or C₃-C₁₄ aryl.Particularly, riboses are ribose, 2′-deoxyribose, 2′,3′-dideoxyribose,3′-haloribose (such as 3′-fluororibose or 3′-chlororibose) and3′-alkylribose, arabinose, 2′-O-methyl ribose, and locked nucleosideanalogs (e.g., WO 99/14226), although many other analogs are also knownin the art.

The term “nucleic acid” as used herein can refer to the nucleic acidmaterial itself and is not restricted to sequence information (i.e. thesuccession of letters chosen among the five base letters A, C, G, T, orU) that biochemically characterizes a specific nucleic acid, forexample, a DNA or RNA molecule. Nucleic acids described herein arepresented in a 5′→3′ orientation unless otherwise indicated.

As used herein, the term “reporter moiety” refers to a moiety that canbe directly or indirectly detected. Detectable reporters include, butare not limited to affinity tags (e.g., biotin, avidin, streptavidin,etc.) and epitope tags recognized by an antibody. As used herein an“indirectly detectable” reporter necessitates interaction or reactionwith either another substrate or reagent for detection. Indirectlydetectable reporters include, but are not limited to affinity tags(needs affinity partner), eptiope tags (needs antibody), and enzymesubstrate (needs enzyme).

As used herein, the phrase “wherein a reporter moiety is attached tosaid linker” means that the reporter moiety is attached to the linkerattached to the nucleobase of the nucleotide analog. For example, areporter moiety appended to the nucleobase via an aminoallyl group orother linking group attached to the nucleobase is “linked to thenucleobase.” Linkers useful according to the invention are describedherein below.

As used herein, the term “sugar analog” refers to analogs of the sugarribose. Exemplary ribose sugar analogs include, but are not limited to,substituted or unsubstituted furanoses having more or fewer than 5 ringatoms, e.g., erythroses and hexoses and substituted or unsubstituted 3-6carbon acyclic sugars. Typical substituted furanoses and acyclic sugarsare those in which one or more of the carbon atoms are substituted withone or more of the same or different —R, —OR, —NRR or halogen groups,where each R is independently —H, (C₁-C₆) alkyl or (C₁-C₁₄) aryl.Examples of substituted furanoses having 5 ring atoms include but arenot limited to 2′-deoxyribose, 2′-(C₁-C₆)alkylribose,2′-(C₁-C₆)alkoxyribose, 2′-(C₅-C₁₄)aryloxyribose, 2′,3′-dideoxyribose,2′,3′-didehydroribose, 2′-deoxy-3′-haloribose, 2′-deoxy-3′-fluororibose,2′-deoxy-3′-chlororibose, 2′-deoxy-3′-aminoribose,2′-deoxy-3′-(C₁-C₆)alkylribose, 2′-deoxy-3′-(C₁-C₆)alkoxyribose,2′-deoxy-3′-(C₅-C₁₄)aryloxyribose,3′-(C₁-C₆)alkylribose-5′-triphosphate,2′-deoxy-3′-(C₁-C₆)alkylribose-5′-triphosphate,2′-deoxy-3′-(C₁-C₆)alkoxyribose-5′-triphosphate,2′-deoxy-3′-(C₅-C₁₄)aryloxyribose-5′-triphosphate,2′-deoxy-3′-haloribose-5′-triphosphate,2′-deoxy-3′-aminoribose-5′-triphosphate,2′,3′-dideoxyribose-5′-triphosphate or2′,3′-didehydroribose-5′-triphosphate. Further sugar analogs alsoinclude so called locked nucleic acids (LNAs) having the structure

and those described in Wengel, et al. WO 99/14226, incorporated hereinby reference.

The term “purine nucleobase” refers to a compound comprising a purinering. It will be understood that a purine nucleobase can be anynaturally occurring purine nucleobase known in the art, including butnot limited to, adenine and guanine. The term “purine nucleobase analog”refers to natural, synthetic or derivative chemical compoundsstructurally similar to a naturally occurring purine in structure and/orfunction and is capable of forming a covalent bond to a sugar or sugaranalog. Examples of purine nucleobase analogs (in the form ofnucleobases, nucleosides or nucleotides), for which preparatory methodsor commercial sources can be identified and can be found by suitablestructure searching in available databases such as Chem. AbstractsService (CAS), SciFinder, and the like.

The term “pyrimidine nucleobase” refers to a compound comprising apyrimidine ring. It will be understood that a pyrimidine nucleobase canbe any naturally occurring pyrimidine nucleobase known in the art,including but not limited to, uracil, thymine and cytosine. The term“pyrimidine nucleobase analog” refers to natural, synthetic orderivative heterocyclic compounds comprising at least one ring nitrogenatom capable of forming a covalent bond to a sugar or sugar analog.

Examples of pyrimidine nucleobase analogs (in the form of nucleobases,nucleosides or nucleotides), for which preparatory methods or commercialsources can be identified and can be found by suitable structuresearching in available databases such as Chem. Abstracts Service (CAS),SciFinder, and the like, include but are not limited to the followingexemplary structures:

As used herein, the term “polynucleotide” refers to polymers of naturalnucleotide monomers or analogs thereof, including double and singlestranded deoxyribonucleotides, ribonucleotides, α-anomeric formsthereof, and the like. The terms “polynucleotide”, “oligonucleotide” and“nucleic acid” are used interchangeably. Usually the nucleoside monomersare linked by internucleotide phosphodiester linkages, where as usedherein, the term “phosphodiester linkage” refers to phosphodiester bondsor bonds including phosphate analogs thereof, and include associatedcounterions, including but not limited to H⁺, NH₄ ⁺, NR₄ ⁺, Na⁺, if suchcounterions are present. A polynucleotide may be composed entirely ofdeoxyribonucleotides, entirely of ribonucleotides or chimeric mixturesthereof.

As used herein, the term “terminator” means an enzymaticallyincorporatable nucleotide which prevents subsequent incorporation ofnucleotides to the resulting polynucleotide chain and thereby haltspolymerase-mediated extension. Typical terminators lack a 3′-hydroxylsubstituent and include 2′,3′-dideoxyribose, 2′,3′-didehydroribose, and2′,3′-dideoxy-3′-haloribose, e.g. 3′-deoxy-3′-fluoro-ribose or2′,3′-dideoxy-3′-fluororibose, for example. Alternatively, aribofuranose analog can be used, such as2′,3′-dideoxy-β-D-ribofuranosyl, β-D-arabinofuranosyl,3′-deoxy-β-D-arabinofuranosyl, 3′-amino-2′,3′-dideoxy-β-D-ribofuranosyl,and 2′,3′-dideoxy-3′-fluoro-β-D-ribofuranosyl (see, for example,Chidgeavadze et al., Nucleic Acids Res., 12:1671-1686 (1984), andChidgeavadze et al. FEB. Lett., 183:275-278 (1985)). Nucleotideterminators also include reversible nucleotide terminators (Metzker etal. Nucleic Acids Res., 22(20):4259 (1994)).

As used herein, the term “nonextendable” or “3′ nonextendable” refers tothe fact that a terminator is incapable, or substantially incapable, ofbeing extended in the 3′ direction by a template-dependent DNA or RNApolymerase.

As used herein, the term “void” refers to the absence of a substituentgroup at the R₃ position of the cap analog. The lack of a substituentgroup results in no positive charge on the imidazole ring. In someembodiments the substituent group may be a CH₃ group. When the CH₃ groupis present, there is a positive charge on the imidazole ring.

Reporter Moiety Labeled Dinucleotide Cap Analogs:

Throughout this disclosure, various linkers and reporter moieties arepresented. It should be understood that the illustrated linkers andreporter moieties are presented merely for convenience and brevity andshould not be construed as an inflexible limitation of the scope of theembodiments claimed herein. Accordingly, the illustration of a labeleddinucleotide cap analog with a particular linker or reporter moiety isnot limited to only the linker or reporter moiety so illustrated. Forexample, the illustrated linker could be replaced with an aminoallyl([—CH₂]—CH₂NH₂) where n=2-18, a secondary amine or an alkyl (C₃-C₁₀)NH₂chain. Furthermore, the alkyl chain can comprise three to ten chainatoms with a terminal primary amine and the linker can be a cleavable orcan be a non-cleavable linker. Likewise, the reporter moiety can be anymoiety capable of binding to a substrate, for example, a magnetic bead,a chromatography column bound with, for example, avidin, streptavidin,antigen, antibody, and the like. The reporter moiety can be an affinitytag or an epitope tag. A reporter moiety such as biotin can be replacedwith other affinity tags such as iminobiotin, avidin, and streptavidin.Non-limiting examples of biotin molecules that can comprise the reportermoiety include C₅-C₂₀-biotin, SS-biotin, XX-biotin, and NHS estercompounds thereof.

The novel dinucleotide cap analogs described herein are useful for,among other things, specifically transcribing the DNA of a molecule ofinterest to mRNA. The dinucleotide cap analog composition generallycomprises:

wherein: B is a nucleobase; R₁ is selected from a halogen, OH, and OCH₃;R₂ is selected from H, OH, and OCH₃; R₃ is CH₃ or void; R₄ is NH₂; R₅ isH; and n is 1, 2 or 3; wherein a linker is attached to one of R₁, R₂,R₄, R₅, or B.

As highlighted by the above structure, the carbon atoms are numbereddifferently. Specifically the carbon atom numberings include primes. Thenumbering system of the nucleobase heterocyclic rings lack a prime andthe positions on the ribose are given a prime (′).

The nucleobase can be a nucleobase or nucleobase analog that isoperative in accordance with the various compositions and methodsdescribed herein. In some embodiments, the nucleobase can be a purine,purine analog, pyrimidine, pyrimidine analog and natural, synthetic andderivatives thereof. In some embodiments, the nucleobase can be adenine,adenine analogs and natural, synthetic and derivatives thereof. In someembodiments the nucleobase can be uracil, uracil analogs and natural,synthetic and derivatives thereof. In some embodiments, the nucleobasecan be guanine, guanine analogs and natural, synthetic and derivativesthereof. In some embodiments, the nucleobase can be cytosine, cytosineanalogs and natural, synthetic and derivatives thereof. In someembodiments, the nucleobase can be thymine, thymine analogs and natural,synthetic and derivatives thereof.

In various embodiments, the nucleobase is a purine, a 7-deazapurine, apyrimidine, or a nucleobase analog. In some embodiments, the nucleobaseis selected from the group comprising: adenine, cytosine, guanine,thymine, uracil, 7-deazapurines, 9-deazapurines, hypoxanthine,thizaolo[4,5-d]pyrimidines, pyrazolol[3,4-d]pyrimidine, pyrazin-2-ones,imidazol[1,5-a]1,3,5 trazinones, imidazo[4,5-d]pyrazines,1,2,4-triazine, pryridazine, and 1,3,5 triazine.

In various embodiments the cap analog can also have novel substituentgroups at the 2′ and/or 3′ positions of the ribose ring which alsoresults in attaching of the cap on the RNA in the forward orientation.In some embodiments the attachment of fluorine or methoxy at the2′-position (R₁) of the ribose ring has been shown to improve bothcapping efficiency and transcription efficiency. In some embodiments theattachment of methoxy or a deoxy substituent at the 3′-position (R₂) ofthe ribose ring has been shown to improve both capping efficiency andtranscription efficiency. In some embodiments the N7-position of theguanine is methylated. FIG. 1 provides an example of the generalstructure of a biotin-labeled mCAP analog, m⁷G[5′]pppp[5′]U—S—S-Biotin.As evidenced by FIG. 1, the dinucleotide cap analog has the capabilityto attach to an RNA transcript and have attached to the cap, forexample, a biotin reporter moiety to use in isolation of the resultingcapped transcript. In various embodiments, the N7-position on theguanine nucleotide is methylated, the R₂ position can be hydroxyl,methoxy or deoxy and n=2 such that the triphosphodiester bond of theBiotin-11-UTP is coupled to the Imidizolide m⁷GMP.

The linker can encompasses any modifying group added to the dinucleotidecap that is operative in accordance with the various compositions andmethods described herein. In various embodiments the linker is achemical entity or entities which provide conjugation between thedinucleotide cap and the reporter moiety. In some embodiments the linkercan have a first end connected to the dinucleotide cap and a primaryamine second end which connects to the reporter moiety having an NHSester form. In some embodiments the linker can be attached to thenucleobase at the N-4 or C-5 position of the nucleobase when thenucleobase is a pyrimidine, or at the C-2, C-6, or C-8 position of apurine nucleobase. In the case of a modification at the C-2, C-6 or C-8position, the linker is an N. In some embodiments the linker can beattached to the C-2′ or C-3′ position of the pentose ring. When attachedto the C-2′ or C-3′ position, the modification is the replacement of the—OH group to an O, an S, an N and so on, atom.

In some embodiments useful linkers include, but are not limited to N, S,and O, an aminoallyl ([—CH₂]_(n)CH₂NH₂) where n=2-18, a secondary amineand an alkyl (C₃-C₁₀)NH₂ chain. Linkers can include, for example, analkyl, allyl, or alkynyl amine modifying group attached to thenucleobase. As an alternative, linkers can include one or more ethyleneoxy moieties. In some embodiments linkers can be cleavable ornon-cleavable. In some embodiments non-cleavable linker examplesinclude, but are not limited to C₃ to C₁₀ atom chain molecules,aminoallyl and the like. In some embodiments FIG. 2 provides an exampleof non-cleavable linkers with biotin as an affinity tag. FIG. 3illustrates the synthesis of m⁷G[5′]pppp[5′]U-18-biotin with anon-cleavable linker.

In some embodiments examples of cleavable linkers include, but are notlimited to, disulfide bonds. The disulfide bond (S—S) can be cleavedunder mild reducing agents such as 50 mM dithiothreitol (DTT), orTris(2-carboxyethyl)phosphine hydrochloride, (TCEP), or 100 mM2-Mercaptoethanol, and or 1% Sodium borohydride (Shimkus, M., et al.Proc. Natl. Acad. Sci. USA 82, 2593-2597, (1985), Dawson, B. A., et al.J. Biol. Chem. 264(22), 12830-12837 (1989), Kirkley, T. L., Anal.Biochem., 180, 231-236 (1989), Andrews, P. C., Dixon, J. E., Anal.Biochem., 161, 524-528 (1987), Schonberg, A., Chem. Ber., 163-164(1935), Rauhut, M., et. al., JACS, 81, 1103-1107 (1959)). FIG. 4illustrates the synthesis of m⁷G[5′]pppp[5′]U—S—S-biotin which comprisesa disulfide cleavable linker.

The reporter moiety can encompasses any detectable group added to thelinker who is attached to the dinucleotide cap that is operative inaccordance with the various compositions and methods described herein.In some embodiments the reporter moiety can be any moiety capable ofbinding to a substrate. In some embodiments the reporter moiety can beselected from an affinity tag and an epitope tag recognized by anantibody. In some embodiments, examples of moieties used in theisolation of capped RNA include, but are not limited to a magnetic beadcoated with an affinity tag, a chromatography column bound with, forexample, avidin, streptavidin, antigen, antibody, and the like. In someembodiments, the affinity tag can be selected from biotin, iminobiotin,avidin, and streptavidin. Non-limiting examples of biotin molecules thatcan comprise the reporter moiety include C₅-C₂₀-biotin, SS-biotin,XX-biotin, and NHS ester compounds thereof. The attachment of biotinreporter moieties and the NHS esters thereof is facilitated by thepresence of a primary amine within the nucleobase at the 2′ or 3′position which is modified on the pentose ring. The length of the linkerarm varies, between at least a C₄-C₁₅ chain length depending upon theapplication.

In order to improve capping efficiency, the resulting transcriptionyield and the subsequent translation of the transcribed protein, thepresent application teaches chemically convenient and reproduciblemethods for the synthesis of modified cap analogs which can be isolatedand purified following transcription of the mRNA and methods to use thepurified, capped mRNAs in transfection, translation, proteinidentification, therapeutic and disease diagnostic and prognosticapplications.

An additional embodiment of the invention relates to the administrationof a composition which generally comprises an active ingredientformulated with a pharmaceutically acceptable excipient. Excipients mayinclude, for example, sugars, starches, celluloses, gums, and proteins.Various formulations are commonly known and are thoroughly discussed inthe latest edition of Remington's Pharmaceutical Sciences (MaackPublishing, Easton Pa.). Such compositions may consist of novel capanalogs, antibodies to novel cap analogs, and mimetics, agonists,antagonists, or inhibitors of novel cap analogs.

In various embodiments, the compositions described herein, such aspharmaceutical compositions, may be administered by any number of routesincluding, but not limited to, oral, intravenous, intramuscular,intra-arterial, intramedullary, intrathecal, intraventricular,pulmonary, transdermal, subcutaneous, intraperitoneal, intranasal,enteral, topical, sublingual, or rectal means.

The design and synthesis of novel cap analogs such asm^(7[)5′]Gpppp[5′]U-18-Biotin with a non-cleavable linker (FIG. 2) andm7[5′]Gppp[5′]U—S—S-Biotin with a cleavable linker (FIG. 4), in whichvarious moieties at the 2′ and 3′ positions on the ribose ring have beensubstituted are presented. Each reporter moiety labeled RNA cap analogfinds utility in isolation of the capped transcript and in subsequenttransfection, therapeutics, diagnostics, prognostics, or proteintranslation experiments.

Structures were confirmed by ¹H NMR and ³¹P NMR. Transcripts producedwith T7 RNA polymerases using “anti-reverse” cap analogs (ARCAs), with alinker or a linker plus a biotin reporter moiety were of the predictedlength and indistinguishable in size and homogeneity from those producedwith m⁷GppppG.

Therapeutic & Diagnostic Applications of Novel Cap Analogs:

In more recent years, the use of capped RNA for therapeutic purposes hasbeen studied. Mainly it has the potential to be used to generatevaccines against infectious diseases or cancers (Sullenger and Gilboa,Nature, 418, 252-258, (2002). Capped RNA is used to producenon-infectious particles of Venezuelan Equine Encephalitis viruscontaining an RNA encoding immunogen. These non-replicating viralparticles are injected into humans where they can enter host cells. Oncein the host cell, the viral particles dissociate and the mRNA encodingthe immunogen is translated into protein. These proteins can induce animmune response. These types of vaccines are in development for humanimmunodeficiency virus (HIV), feline immunodeficiency virus, humanpapilloma virus type 16, tumors, lassa virus, Ebola virus, Marburgvirus, anthrax toxin from Bacillus anthraces, and botulinum toxin(Burkhead et al., Vaccine, 21(3-4), 258-268, (2002); Davis et al., IUBMBLife, 53(4-5), 209-211 (2002); Eiben et al., Cancer Res., 62(20),5792-5799 (2002); Hevey et al., Virology, 251(1), 28-37, (1998); Pushkoet al., J. Virol., 75, 11677-11685, (2001); Pushko et al., Virology 239,389-401, (1997); Lee et al., Infect. Immun., 69, 5709-5715, (2001); Leeet al., Infect Immun., 71, 1491-1496, (2003)).

These vaccine strategies will require large quantities of capped RNA.Developing methods to synthesize and purify capped RNA will be importantto make these vaccines commercially feasible. As well, strategies toincrease the percentage of full length capped RNA in a transcriptionreaction leading to a more homogenous product will be preferred in thevaccine industry as highly pure components are usually required forhuman use. In addition, researchers prefer to use products that are aspure as possible to minimize the number of variables in an experiment.As well, the purer the product, the more potent it is. Currentprotocols, enabling the production of about 1 mg/mL of capped RNA, aresimply insufficient for the scale of production needed for theseapplications (Frank Grunebach et al Cancer Immunol. Immunother., 54,517-525, (2005); Sullenger and Gilboa, Nature, 418, 252-258, (2002).

Another approach in use is to isolate dendritic cells from a patient andthen to transfect the dendritic cells with capped RNA encodingimmunogen. The dendritic cells translate the capped RNA into at leastone protein that induces an immune response against this protein. In asmall human study, immunotherapy with dendritic cells loaded with CEAcapped RNA was shown to be safe and feasible for pancreatic cancerpatients (Morse et al. Int. J. Gastrointest. Cancer, 32:1-6, (2002)). Itwas also noted that introducing at least one single capped RNA speciesinto immature dendritic cells induced a specific T-cell response (Heiseret al. J. Clin. Invest., 109:409-417, 2002).

Those having ordinary skill in the art will understand that manymodifications, alternatives, and equivalents are possible. All suchmodifications, alternatives, and equivalents are intended to beencompassed herein.

Materials and Methods Reagents

All of the reagents and solvents are used as such without furtherpurification, unless otherwise stated. Guanosine 5′-diphosphate,Dimethyl sulfate, anhydrous dimethylformamide, 2,2′-dithiodipyridine(Aldrithiol), Triphenylphosphine, trimethylphosphate ((OMe)₃P),phosphorous oxychloride, phosphorous pentoxide, orthophosphoric acid,anhydrous methylene chloride, dichloromethane, Tributylamine, andanhydrous pyridine were purchased from Sigma-Aldrich Co.3′-O-Me-Guanosine is available from Chemgene, Boston, Mass. ImidazolideGMP, Imidazolide GDP, Imidazolide 2′F-GMP, Imidazolide 3′CF₃-GDP,Imidazolide m⁷GMP, 1M tris(triethylammonium) phosphate, andtributylammonium orthophosphate were made as taught herein or in A.Kore, and G. Parmar, Synthetic Comm., 36:3393-3399, (2006), incorporatedherein by reference in its entirety. Allylamine UTP (AA-UTP) and UTP TEAwere obtained from Ambion Inc., an Applied Biosystems business, Austin,Tex.

Ezlink-Sulfo-NHS S—S biotin and Ezlink-Sulfo-NHS LC-LC biotin were fromPierce (Rockford, Ill.). Biotin-XX, SE, Biotin-12, SE, and Biotin-X, SEused to make Bio-18-UTP, Bio-16-UTP and Bio-11-UTP, respectively, werefrom Biotium (Hayward, Calif.).

The cap analogs were analyzed by ¹H NMR and ³¹P NMR (Bruker Avance), ¹Hwas collected at 400.1446006 MHz by using D₂O solvent and the ³¹P wascollected at 161.9968531 MHz by using D₂O solvent. Mass Spectroscopy wasperformed on an Applied Biosystems/Sciex, MDX API 150 model andMALDI-TOF was performed on an Applied Biosystems, Voyager DE-PRO model.Analytical HPLC was performed on a Waters, Alliance instrument usingHypersil SAX columns, 5 μm, 250 mm×4.6 mm (Alltech Associates Inc.Deerfield, Ill.).

EXAMPLES

Synthesis of a dinucleotide cap analog is disclosed in US patentapplication 2005/0287539, incorporated herein by reference. Thesynthesis of novel cap analog compositions which improve cappingefficiency and yield of transcribed RNA have been described in PCTpatent application WO 07 15896, incorporated herein by reference. Suchcapped RNA analogs have been shown to improve transcription andtranslation efficiency.

Aspects of the present teachings may be further understood in light ofthe following examples, which should not be construed as limiting thescope of the present teachings in any way.

While the present teachings are described in conjunction with variousembodiments, it is not intended that the present teachings be limited tosuch embodiments. On the contrary, the present teachings encompassvarious alternatives, modifications, and equivalents, as will beappreciated by those of skill in the art.

Example 1 Synthesis of 7-Methyl Guanosine 5′-diphosphate

In a clean, dry 2000 mL round bottom flask equipped with a stifling barand under a stream of argon slowly dissolve dry and finely powderedguanosine 5′-diphosphate (1), (10.0 g, 20.5 mmol), either in free acidor sodium as a counter ion form, in 200 mL water, adjusting pH to 4.0with glacial acetic acid. Dimethyl sulfate (20 mL, 119.04 mmol) was thenadded over a period of one hour with constant stirring at roomtemperature and the reaction continued for an additional hour duringwhich time a decrease in pH was observed but pH was kept between pH 3.8to 4.0 by drop-wise addition of 10 mM NaOH and methylation was monitoredby analytical HPLC for progress. Methylation was determined to be 98%complete within 2 hr. After 2 hr, the reaction mixture was extractedwith CHCl₃(3×200 mL) to remove unreacted excess dimethyl sulfate.

The resulting aqueous layer was further evaporated on a rotaryevaporator to remove any chloroform traces, and then further diluted to1.5 L with water and loaded on an anion exchange resin, i.e., DEAESepharosa fast flow packed in a BPG 100 column (Amersham GE, Piscataway,N.J., USA). BPG (biological process glass) 100 specification: 100/500column (100 mm in diameter and 50 cm in height), packed with DEAESepharosa fast flow resin to the bed volume of 400 mm. The desiredcompound was eluted by using four bed volumes of gradient from 0 to 80%of 1 M TEAB buffer (triethylammonium bicarbonate), pH 7.5, at a flowrate of 100 mL/min, using AKTA purifier 100 FPLC (Amersham GE). At 45%TEAB buffer, 7-methylguanosine 5′-diphosphate (m⁷GDP) was eluted as alarge broad peak, with a strong ultraviolet absorbance at 254 nm. Theresidual bicarbonate was removed by co-evaporating with methanol, 3×600mL. The resulting residue was transferred to a centrifuge tube, and 8.9g sodium perchlorate dissolved in 1.1 L acetone was added and cooled 2hr at 4° C. The resulting mixture was centrifuged and the supernatantliquid was discarded. The precipitate was ground with a new portion ofacetone, cooled and centrifuged, repeating once. The precipitate wasdried in a vacuum desiccator over P₂O₅. The resulting amorphous whitepowder was 7 methyl-guanosine 5′-diphosphate. Taken from Kore, A. andParmar, G. Nucleosides, Nucleotides, and Nucleic Acids, 25:337-340,2006, incorporated herein by reference in its entirety.

Example 2 Synthesis of Nucleoside-5 ‘-diphosphates

Although the following procedure illustrates synthesis ofguanosine-5’-diphosphate, one of skill in the art would be able to usethe procedure for the synthesis of adenosine-5′-diphosphate,uridine-5′-diphosphate, and cytidine-5′-diphosphate, and analogs andderivatives thereof. In a clean, dry 500 mL round bottom flask equippedwith a stifling bar the triethylammonium salt of guanosine5′-monophosphate (10.0 g, 21.5 mmol) in anhydrous dimethylformamide (200mL) was stirred together, triethylamine was added (2.4 mL, 142.8 mmol)and allowed to stir for 5 min, followed by the addition of Imidazole(5.86 g, 86.1 mmol), 2,2′-dithiodipyridine (7.4 g, 33.58 mmol), andtriphenylphosphine (8.9 g, 33.9 mmol). Stirring was continued for 2 hrat room temperature. The reaction was allowed to go to completion asdetermined by HPLC and then poured slowly into a mixture of sodiumperchlorate (7 g) in acetone (1500 mL), and then cooled for 30 min at 4°C. The reaction mixture was centrifuged, discarding the supernatant.Traces of imidazole and triphenylphosphine were removed by grinding thesolid with a new portion of acetone (400 mL), cooling and againcentrifuged, repeating once. The precipitate was dried in a vacuum ovenover P₂O₅ at 24° C. (30 mbar pressure). Theribonucleoside-5′-phosphoroimidazolide thus obtained was dissolved indimethylforamide (200 mL), and a 1 M solution of tributylammoniumorthophosphate in dimethylformamide (80 mL) was added drop-wise to thevigorously stirred mixture over a period of 30 min Zinc chloride (2 g,14.67 mmol) was added and the reaction mixture stirred at roomtemperature for 3 hr. Completion of the reaction was monitored by HPLC.The reaction mixture was quenched with water (50 mL) and extracted withchloroform (3×200 mL), concentrated in a rotary evaporator and thenpurified by application to an anion exchange resin.

Purification by column chromatography was accomplished with a DEAESepharose fast flow resin packed in an XK 50/60 column (50 mm diameterand 60 cm long) (Amersham GE). The desired compound was eluted by usingfour bed volumes of gradient from 0 to 80% of 1 M TEAB buffer pH 7.5(triethylammonium bicarbonate) at a flow rate of 20 mL/min, using anAKTA purifier 100 FPLC (Amersham GE). At 55% TEAB buffer, the desiredproduct (nucleoside-5′-diphosphate) was eluted as a large broad peak,with a strong ultraviolet absorbance at 254 nm. Thenucleoside-5′-diphosphate-containing fractions were pooled andevaporated using a rotary evaporator to give triethylamine salt of thedesired diphosphate compound. Taken from A. Kore, and G. Parmar,Synthetic Comm., (2006) supra.

Example 3 Synthesis of 3′-O-Methyl Guanosine Monophosphate (3′-O-Me-GMP)TEA Salt

In a clean, dry 500 mL round bottom flask equipped with a stifling barand under a stream of argon slowly add dry and finely powdered3′-O-Me-Guanosine, (6 g, 20 mmol) to a mixture of trimethylphosphate((OMe)₃P) (50 mL) and phosphorous oxychloride (POCl₃) (6 mL, 60 mmol) at0° C. in small portions with continuous stifling under argon. Themixture was kept at 0-4° C. and allowed to stir at least 19 hrs. Diethylether (200 mL) was added to extract the excess phosphorous oxychlorideand to simultaneously precipitate the3′-O-methylguanosine-5′-phosphodichloridate, which was then pelleted bycentrifugation and dissolved in 100 mL ice-cold 5% NaHCO₃ in water. Theresulting aqueous solution was adjusted to pH ˜1.5 using 1 N NaOH. Afterstifling at 0-4° C. for an additional 20 hr, the pH was adjusted to 7.0and the resulting mixture was applied to a column of DEAE Sephadex A25.The column was washed with 5 mmol TEAB buffer, pH 7.5 and then elutedwith freshly prepared 1M Triethylammonium bicarbonate (TEAB) buffer, pH7.5. Fractions containing the 3′-O-Me GMP TEA salt were pooled,concentrated to dryness.

Example 4 Synthesis of Imidazolyl GMP

Commercially available disodium salt of GMP was passed through a DEAESepahadex column and eluted with ammonium bicarbonate buffer (pH 7.5) toobtain the triethylamine (TEA) salt of GMP. To a dried TEA salt of GMP(4.0 g, 7.1 mmol) was added aldrithiol (3.13 g, 14.19 mmol), imidazole(2.42 g, 35.49 mmol), triphenylphosphine (3.72 g, 14.19 mmol) and 50 mLof anhydrous DMF. To this solution was added 1.09 mL (7.81 mmol) oftriethylamine and the solution was stirred overnight. 10 μL of 20 timesdiluted reaction solution was injected into a Waters HPLC (Hypersil SAXColumn, 5 μm, 250×4.6 mm, Buffer A: 50 mmol Ammonium PhoshpateMonobasic, pH 2.8; Buffer B: 750 mmol Ammonium Phoshpate Monobasic, pH3.7). The HPLC chromatogram showed the presence of a new peakcorresponding to imidazolyl GMP and the absence of TEA GMP. The reactionmixture was centrifuged and the supernatant solution was collected andkept at 4° C. To a solution of 5 g of NaClO₄ in 500 mL of acetonemaintained at −20° C. for 2 hr was added the supernatant solution toprecipitate imidazolyl GMP (ImGMP). The heterogeneous solution wascentrifuged and the supernatant solution was discarded. The precipitatewas washed with 3×200 mL of acetone to remove yellow coloredimpurities/byproducts and residual sodium perchlorate. Imidazolyl GMP(ImGMP) (3.5 g, 93.31%) was dried under vacuum over P₂O₅ for a few hoursand immediately stored at −20° C.

Example 5 Synthesis of 3′-O-Me-GMP Imidazolide

In a clean, dry 1 L round bottom flask equipped with a stifling bar andunder a stream of argon slowly add anhydrous DMF (144 mL) and thetriethylamine (0.933 mL, 9.23 mmol) allow to stir for at least 5 min Tothis slowly was add the dry and finely powdered 3′-O -Me-GMP TEA salt,(3.5 g, 7.34 mmol) in small portions with continuous stifling underargon. Thereafter the Imidazole (2.05 g, 30.1 mmol), Aldrithiol (2.65 g,12.02 mmol), and triphenylphosphine (3.13 g, 11.9 mmol) were added andthe reaction allowed to stir at room temperature for at least 2-3 hr,during which the reactants became soluble making the reaction appearclear yellow colored. Upon completion, sodium perchlorate (3.0 g, 24.5mmol) dissolved in acetone with continuous stirring and to this mixture,slowly added, was the reaction mixture. This mixture was then poured intwo 1 L Nalgene bottles and cooled in a refrigerator at −80° C. for 30minutes. The mixture was then subjected to centrifugation at 3000 rpmfor 15 min and the supernatant was discarded. The precipitate was groundwith a new portion of acetone and centrifuged. The process was repeatedonce more and the precipitate was dried in a vacuum desiccator overphosphorous pentoxide, yielding 3′-O-Me-GMP Imidazolide.

Example 6 Synthesis of 3′O-Me-GDP TEA salt Synthesis ofTris(triethylammonium) phosphate linker

Anhydrous orthophosphoric acid (22.5 g, 229.59 mmol) was added to 50 mLof anhydrous methylene chloride in a clean, oven dried 250 mL flaskequipped with a stirring bar. Tributylamine (54.6 mL, 229.6 mmol) wasthen added into the solution drop wise through an addition funnel over aperiod of 30 min The mixture was left stifling for 1 hr. CH₂Cl₂ was thenevaporated and the reaction residue was co-evaporated with 3×30 mL ofanhydrous pyridine and then 2×30 mL of anhydrous DMF. TheTris(triethylammonium) phosphate linker product was dissolved in 100 mLanhydrous DMF so as to have a final concentration of 1 M, and storedover 4 Å molecular sieves at 4° C.

In a clean, dry 1 L round bottom flask equipped with a stirring bar andunder a stream of argon anhydrous DMF (40 mL) was slowly added andstirred for at least 5 minutes. To this was slowly added finely powdered3′-O-Me-GMP Imidazolide (Ex. 5), (3.0 g, 7.04 mmol) in small portionswith continuous stirring under argon. Zinc chloride (2.0 g, 14.6 7 mmol)was added in small portions until the contents were dissolved.Thereafter, the tris(triethylammonium) phosphate linker and 1 Mtributylammonium orthophosphate (40 mL) was added slowly to the reactionmixture under argon and the reaction was allowed to stir at roomtemperature for 5 hr. The reaction when followed on HPLC showingcomplete conversion of the starting material, 3′-O-Me-GMP Imidazolide(Ex. 5) to its corresponding diphosphate. Upon completion, the reactionwas supplemented with water, 100 mL, and the resultant mixture wasextracted with chloroform (3×250 mL), subjected to volume reduction(˜100 mL) by evaporation and applied to DEAE Sephadex A25 column,eluting with a linear gradient of freshly prepared 1 M TEAB, pH 7.5. Thefractions containing the pure 3′O-Me-GDP TEA salt were eluted, combinedand evaporated to dryness.

Example 7 Synthesis of m₂ ^(7,3′O) GDP

To a stirred solution of 3′-O-Me-GDP TEA salt (Ex. 6), (4.0 g, 6.1 mmol)in 100 mL of nuclease free water, concentrated glacial acetic acid wasslowly added to adjust the pH of the solution to 4.0; dimethyl sulfate((Me)₂SO₄) (20 mL, 210 mmol) was slowly added drop wise over a period of60 min, while maintaining the pH˜4.0-4.5 with 50 mM NaOH. The reactionwas allowed to stir at room temperature for 2 hr and methylation wasmonitored by HPLC. After 2 hr, the reaction mixture was extracted withCHCl₃ (3×250 mL) to remove unreacted dimethyl sulfate. The aqueous layerwas applied to a DEAE Sephadex column and the fractions containing theproduct were pooled, evaporated and dried in a vacuum desiccator overphosphorous pentoxide to give m7-3′-O-Me GDP(N-7-Me-3′-O— GDP, m₂^(7,3′O)GDP) as a fine powder.

The examples disclosed herein for the synthesis of novel dinucleotidecap analogs illustrate the use of guanine and uracil nucleobases in thedinucleotide RNA cap. The examples describe illustrated cap analogs,however, there are additional cap analogs conceived which will alsofunction in practicing the invention as illustrated. One of skill in theart will recognize that any nucleobase, nucleobase analog, rathernatural, synthetic or a derivative thereof as well as any sugar or sugaranalog or linker could be used and is contemplated herein.

Example 8

The coupling reaction of imidazolyl m⁷GMP with a correspondingnucleobase modified nucleotide in the presence of ZnCl₂ provides thecorresponding cap analog as shown in the above scheme.

TABLE 1 Cap Analogs with Linkers (Nos. 1-6), Linker + Reporter Moiety(Nos. 7-29), Control Cap (No. 30) No Abbreviation R₁(2′) R₂(3′) R₃ R₄ R₅ARCA 1 G[5′]pppp[5′]U-Aminoallyl & OH OH void NH₂ H NoG[5′]pppp[5′]C-Aminoallyl 2 m⁷G[5′]pppp[5′]U-Aminoallyl & OH OH CH₃ NH₂H Yes m⁷G[5′]pppp[5′]C-Aminoallyl 3 m₂ ^(7,3′O)G[5′]pppp[5′]U-Aminoallyl& OH OCH₃ CH₃ NH₂ H Yes m₂ ^(7,3′O)G[5′]pppp[5′]C-Aminoallyl 4 m₂^(7,2′O)G[5′]pppp[5′]U-Aminoallyl & OCH₃ OH CH₃ NH₂ H Yes m₂^(7,2′O)G[5′]pppp[5′]C-Aminoallyl 5 m^(7,2′F)G[5′]pppp[5′]U-Aminoallyl &F OH CH₃ NH₂ H Yes m^(7,2′F)G[5′]pppp[5′]C-Aminoallyl 6m⁷3′dG[5′]pppp[5′]U-Aminoallyl & OH H CH₃ NH₂ H Yesm⁷3′dG[5′]pppp[5′]C-Aminoallyl 7 G[5′]pppp[5′]U-18-Biotin & OH OH voidNH₂ H No G[5′]pppp[5′]C-18-Biotin 8 m⁷G[5′]pppp[5′]Nuc-18-Biotin OH OHCH₃ NH₂ H No non cleavable linker 9 m₂^(7,3′O)G[5′]pppp[5′]Nuc-18-Biotin OH OCH₃ CH₃ NH₂ H Yes non cleavablelinker 10 m₂ ^(7,2′O)G[5′]pppp[5′]Nuc-18-Biotin OCH₃ OH CH₃ NH₂ H Yesnon cleavable linker 11 m^(7,2′F)G[5′]pppp[5′]Nuc-18-Biotin F OH CH₃ NH₂H Yes non cleavable linker 12 m^(7,)3′dG[5′]pppp[5′]Nuc-18-Biotin OH HCH₃ NH₂ H Yes non cleavable linker 13 m⁷G[5′]pppp[5′]Nuc-S-S-Biotin OHOH CH₃ NH₂ H No disulfide cleavable linker 14 m₂^(7,3′O)G[5′]pppp[5′]Nuc-S-S-Biotin OH OCH₃ CH₃ NH₂ H Yes disulfidecleavable linker 15 m₂ ^(7,2′O)G[5′]pppp[5′]Nuc-S-S-Biotin OCH₃ OH CH₃NH₂ H Yes disulfide cleavable linker 16m^(7,2′F)G[5′]pppp[5′]Nuc-S-S-Biotin F OH CH₃ NH₂ H Yes disulfidecleavable linker 17 m^(7,)3′dG[5′]pppp[5′]Nuc-S-S-Biotin OH H CH₃ NH₂ HYes disulfide cleavable linker 18 m^(7, 8-S-S-Biotin)G[5′]pppp[5′]Nuc OHOH CH₃ NH₂ S-S-Biotin No 19 m₂ ^(7,3′O, 8-S-S-Biotin)G[5′]pppp[5′]Nuc OHOCH₃ CH₃ NH₂ S-S-Biotin Yes 20 m₂ ^(7,2′O, 8-S-S-Biotin)G[5′]pppp[5′]NucOCH₃ OH CH₃ NH₂ S-S-Biotin Yes 21 m₂^(7,2′F, 8-S-S-Biotin)G[5′]pppp[5′]Nuc F OH CH₃ NH₂ S-S-Biotin Yes 22m^(7, 8-S-S-Biotin) 3′dG[5′]pppp[5′]Nuc OH H CH₃ NH₂ S-S-Biotin Yes 23m^(7, 2-S-S-Biotin)G[5′]pppp[5′]Nuc OH OH CH₃ S-S-Biotin H No 24 m₂^(7,3′O, 2-S-S-Biotin)G[5′]pppp[5′]Nuc OH OCH₃ CH₃ S-S-Biotin H Yes 25m₂ ^(7,2′O, 2-S-S-Biotin)G[5′]pppp[5′]Nuc OCH₃ OH CH₃ S-S-Biotin H Yes26 m₂ ^(7,2′F, 2-S-S-Biotin)G[5′]pppp[5′]Nuc F OH CH₃ S-S-Biotin H Yes27 m^(7, 2-S-S-Biotin) 3′dG[5′]pppp[5′]Nuc OH H CH₃ S-S-Biotin H Yes 28m^(7, 2′-S-S-Biotin)G[5′]pppp[5′]Nuc S-S- OH CH₃ NH₂ H Yes Biotin 29m^(7,3′-S-S-Biotin)G[5′]pppp[5′]Nuc OH S-S- CH₃ NH₂ H Yes Biotin 30 m₂^(7,3′O)G[5′]pppp[5′]U OH OCH₃ CH₃ NH₂ H Yes 31 Biotin-18-UTP n/a Nuc =Nucleobase, G = guanine, C = cytosine, U = uracil; UTP = uraciltriphosphate

Table 1 illustrates dinucleotide caps having modifications within atleast one of the component structures comprising: the nucleobase and itssubstituents; the sugar moiety and its substituents; and the number ofphosphate groups linking the nucleotides together. Additionalmodifications can comprise a linker, either cleavable or non-cleavable,and a reporter moiety. Although the reporter moiety indicated is biotin,it is not intended that the present teachings be limited to such anembodiment as other affinity tags can substitute for biotin. On thecontrary, the present teachings encompass various alternatives,modifications, and equivalents, as will be appreciated by those of skillin the art with respect to the reporter moiety, the position of thelinker, the type of linker and the associated substituents on thedinucleotide caps. ARCAs are as indicated.

Example 9

Synthesis of m₂ ^(7,3′O)G[5′]pppp[5′]U (30)

To a stirred solution of UTP TEA salt (0.125 g, 0.17 mmol) and m₂^(7,3′O)ImGMP (0.075 g, 0.17 mmol), the synthesis of which is shown inExample 12, in 5.0 mL dry DMF, zinc chloride (0.046 g, 0.34 mmol) wasadded under nitrogen atmosphere and the reaction mixture was stirred atroom temperature for 14 hr. After 14 hr, the reaction mixture was addedto a solution of EDTA disodium (0.26 g, 0.68 mmol) in 100.0 mL of waterat 0° C. The resulting aqueous solution was adjusted to pH 5.5 andloaded on a DEAE Sephadex column. The desired product was eluted using alinear gradient of 0-1M TEAB and the fractions containing the productwere pooled, evaporated and concentrated to 10.0 mL TEA salt of m₂^(7,3′O)G[5′]pppp[5′]U (30). The resulting 10.0 mL was passed through aStrata-X-AW column and washed with 10.0 mL water followed by 10.0 mLMeOH. Then, the desired compound was eluted with 15.0 mL ofNH₄OH/MeOH/H₂O (Feb. 25, 1973) and the collected solution was evaporatedand dried to give a fine white powder (compound 30). (Yield: 0.078 g,54%). The use of m₂ ^(7,3′O)G[5′]pppp[5′]U as a control for comparisonof yield of in vitro transcription and translation activity in order tocompare results with novel mCAPs and ARCA caps conceived herewith.

Data for Compound 30: ¹H NMR (D₂O, 400 MHz) δ7.94 (d, J=8.0 Hz, 1H),6.04 (d, J=4.4 Hz, 1H), 5.95 (m, 2H), 4.51 (m, 1H), 4.43-4.35 (m, 3H),4.29-4.19 (m, 6H), 4.14 (s, 3H), 3.52 (s, 3H); ³¹P NMR (D₂O, 162 MHz)δ-10.27 (d, J=16.0 Hz)-21.92 (m); MS (m/z): 858 [M]⁺. Used as a controlfor comparison of yield of in vitro transcription and translationactivity.

Example 10 Synthesis of Compounds 1, 2, and 8

Synthesis of G[5′]pppp[5′]U-Aminoallyl (1):

To an anhydrous solution of Imidazolyl GMP (400 mg, 0.78 mmol) andAA-UTP TEA (360.66 mg, 0.389 mmol) was added 4 equivalents of anhydrousZnCl₂ (212.39 mg, 1.56 mmol) and the reaction mixture was stirredovernight. Then, the reaction mixture was stirred with 589.3 mg of EDTAin 25 mL of water for 10 min and the pH of the solution was adjustedwith conc. NaHCO₃ to pH 5.5. The resultant solution was loaded onto aDEAE Sepharose column and eluted with 25-100% triethylammoniumbicarbonate buffer (pH 7.5, 4° C.) to obtain pureG[5′]pppp[5′]U-Aminoallyl (1) (450 mg, 90.89%). The identity of compound(1) was confirmed by LC-MS and NMR spectrum. The molecular weight ofthis compound as revealed by MALDI-TOF is 885.33 Da (Expected Exact Massis 884.03 Da).

Data for Compound (1): ¹H NMR (D₂O, 400 MHz) δ8.09 (s, 1H), 8.02 (s,1H), 6.49 (d, J=16.4 Hz, 1H), 6.37 (m, 1H), 5.91 (d, J=4.0 Hz, 1H), 5.87(d, J=6.0 Hz, 1H), 4.72 (t, J=6.0 Hz, 1H), 4.53 (m, 1H), 4.41-4.22 (m,8H), 3.71 (d, J=6.4 Hz, 2H); ³¹P NMR (D₂O, 162 MHz) δ-9.95 (d, J=16.7Hz, 1P), -10.12 (d, J=16.7 Hz, 1P), -21.40 (m, 2P); MS (m/z): 884[M+H]⁺.

Synthesis of m⁷G[5′]pppp[5′]U-Aminoallyl (2):

To a stirred solution of 300 mg (0.236 mmol) ofG[5′]pppp[5′]U-Aminoallyl (1) was slowly added 2.24 mL (23.6 mmol) ofdimethyl sulfate. During the addition of dimethyl sulfate, the pH of thesolution was maintained ˜4.0 using a solution of concentrated NaOH. Theprogress of the reaction was monitored by analytical anion exchangeHPLC. After the complete disappearance of starting material, the samplewas loaded onto a DEAE Sepharose column and eluted with 25-100%triethylammonium bicarbonate buffer (pH 7.5, 4° C.) to obtainm⁷G[5′]pppp[5′]U-Aminoallyl (2) in 82.36% yield (250 mg). The identityof this compound was confirmed by LC-MS and NMR spectrum. The molecularweight of this compound as revealed by MALDI-TOF is 899.69 Da (ExpectedExact Mass is 899.05 Da).

Data for Compound (2): ¹H NMR (D₂O, 400 MHz) δ8.12 (s, 1H), 6.53 (d,J=16.4 Hz, 1H), 6.44 (m, 1H), 6.00 (d, J=3.6 Hz, 1H), 5.92 (d, J=4.0 Hz,1H), 4.61 (m, 1H), 4.51 (d, J=5.2 Hz, 1H), 4.42-4.24 (m, 8H), 4.12 (s,3H), 3.73 (d, J=6.0 Hz, 2H); ³¹P NMR (D₂O, 162 MHz) δ-10.27 (m, 2P),-21.73 (m, 2P); MS (m/z): 899 [M]⁺.

Synthesis of m⁷G[5′]pppp[5′]U-18-Biotin (8):

150 mg (0.152 mmol) of m⁷G[5′]pppp[5′]U-Aminoallyl (2) was dissolved in5 mL of 0.1 M sodium borate buffer (pH 8.5) and the solution was stirredfor 15 min at room temperature. Immediately before use, a solution of152.62 mg (0.228 mmol) of Biotin XX NHS ester in 2 mL of DMSO wasprepared. To a stirred solution of m⁷G[5′]pppp[5′]U-AA was added BiotinXX NHS ester slowly during a period of 10 min The reaction was allowedto take place for 4 hr at room temperature. After 4 hr, the reactionmixture was loaded onto an AMBERCHROM™ XT20 RP column and eluted with2-50% acetonitrile to obtain pure m⁷G[5′]pppp[5′]U-18-Biotin (8) in90.51% yield (198 mg). The molecular weight of this compound as revealedby MALDI-TOF is 1351.37 Da (Expected Exact Mass 1351.30 Da).

Data for compound (8): ¹H NMR (D₂O, 400 MHz) δ7.92 (s, 1H), 6.46 (m,1H), 6.30 (d, J=16.0 Hz, 1H), 6.01 (d, J=4.0 Hz, 1H), 5.95 (d, J=6.0 Hz,1H), 4.68-4.24 (m, 12H), 4.12 (s, 3H), 3.90 (m, 2H), 3.30 (m, 1H), 3.17(t, J=6.8 Hz, 4H), 2.98 (dd, J=13.0, 5.0 Hz, 1H), 2.77 (d, J=13.2 Hz,1H), 2.31 (t, J=6.8 Hz, 2H), 2.22 (m, 4H), 1.76-1.27 (m, 18H); ³¹P NMR(D₂O, 162 MHz) δ-10.29 (d, J=17.8 Hz, 1P), -10.66 (d, J=17.0 Hz, 1P),-22.08 (m, 2P); MS (m/z): 1351 [M]⁺.

Compounds 1, 2 and 8 are also shown in FIG. 3 which illustrates themethylation of the N7 position of the guanosine by taking compound (1)and reacting it with dimethyl sulfoxide at a pH of 4.0-4.5 to providecompound (2), and the subsequent treatment of compound (2) with sodiumborate buffer at pH 8.5 and Biotin-XX-SE to provide a reporter moietytagged dinucleotide cap as illustrated by compound (8).

Example 11

Scheme to Make Compounds 4, 5, and 6

The coupling reaction of Aminoallyl UTP with m₂ ^(7,2′O)ImGMP orm^(7,2′F)ImGMP or m⁷3′dImGMP in the presence of ZnCl₂ provides thecorresponding compounds 4, 5, and 6, respectively.

Example 12 Preparation of m₂ ^(7,3′O)G[5′]pppp[5′]U-Aminoallyl (3)

(a) Preparation of m₂ ^(7,3′O)ImGMP:(i) Preparation of m₂ ^(7,3′O)GMP:

To a stirred solution of m^(3′O)GMP (1.50 g, 3.14 mmol) in 50.0 mL ofwater, acetic acid was added slowly to adjust the pH of the solution to4.0. To this mixture, dimethyl sulfate (3.0 mL) was added drop wise overa period of 30 min and the reaction mixture was allowed to stir at roomtemperature for 3 hr. As the methylation proceeds, the pH drops down toaround 2.0 and was readjust back to pH 4.0 using 1M NaOH solution. After3 hr, the reaction mixture was extracted with CHCl₃ (3×50) to removeunreacted excess dimethyl sulfate. The collected aqueous solution wasadjusted to pH 5.5 with glacial acetic acid and loaded on a DEAESephadex column. The desired product was eluted using a linear gradientof 0-1 M TEAB, pH 7.5 and the fractions containing the product werepooled, evaporated and dried in vacuum desiccator over phosphorouspentoxide to give a fine white powder of m₂ ^(7,3′O)GMP along withexcess triethylammonium bicarbonate salt (Yield 11.2 g).

(ii) Synthesis of m₂ ^(7,3′O)ImGMP:

To a stirred solution of m₂ ^(7,3′O)GMP (11.2 g) in 50 mL dry DMF,imidazole (1.07 g, 15.7 mmol), triphenylphosphine (1.64 g, 6.28 mmol),aldrithiol (1.38 g, 6.28 mmol) and triethylamine (0.32 g, 3.14 mmol)were added. The reaction mixture was stirred under nitrogen atmosphereat room temperature overnight. Then, the reaction mixture was filteredto obtain a clear filtrate. To a solution of sodium perchlorate (2.0 g)in 100 mL acetone in a centrifuge tube at 0° C., the above clearfiltrate was added slowly for 5 minutes. The resulting mixture wascentrifuged and the supernatant liquid was removed. The solid was groundwith a new portion of acetone (100 mL), cooled, and centrifuged again.This process was repeated twice and the resulting solid was dried in avacuum desiccator over P₂O₅ to give a white powder, m₂ ^(7,3′O)ImGMP(Yield: 0.62 g, 45%-Isolated overall yield based on the starting m₂^(7,3′O)GMP)

(b) Conjugation of AA-UTP with m₂ ^(7,3′O)ImGMP:

The coupling reaction of AA-UTP with m₂ ^(7,3′O)ImGMP in the presence ofZnCl₂ provides the corresponding m₂ ^(7,3′O)G[5′]pppp[5′]U-Aminoallyl(3).

Example 13 Scheme to make G[5′]pppp[5′]U-18-Biotin andG[5′]pppp[5′]C-18-Biotin

Synthesis of GppppU-18-Biotin (7a):

To an anhydrous solution of Imidazolyl GMP (100 mg, 0.195 mmol) andBio-18-UTP TEA (223.73 mg, 0.162 mmol) was added 4 equivalents ofanhydrous ZnCl₂ (88.49 mg, 0.65 mmol) and the reaction mixture wasstirred overnight. The reaction mixture was stirred with 188 mg of EDTAfor 10 min and the pH of the solution was adjusted with conc. NaHCO₃ to5.5. The resultant solution was loaded onto a DEAE Sepharose column andeluted with 25-100% triethylammonium bicarbonate buffer (pH 7.5, 4° C.)to obtain pure GppppU-18-Bio (7) (230 mg, 82.21%). The identity ofcompound 3 was confirmed by LC-MS and NMR spectrum.

Data for compound (7a): ¹H NMR (D₂O, 400 MHz) δ8.12 (s, 1H), 7.88 (s,1H), 6.41 (m, 1H), 6.23 (d, J=16.0 Hz, 1H), 5.96 (d, J=5.6 Hz, 1H), 5.87(d, J=6.4 Hz, 1H), 4.58 (m, 2H), 4.46-4.26 (m, 10H), 3.88 (m, 2H), 3.28(m, 1H), 3.15 (m, 4H), 2.97 (dd, J=13.0, 5.0 Hz, 1H), 2.76 (d, J=13.2Hz, 1H), 2.32-2.19 (m, 6H), 1.73-1.24 (m, 18H); ³¹P NMR (D₂O, 162 MHz)δ-10.25 (d, J=20.4 Hz, 1P), -10.57 (d, J=20.5 Hz, 1P), -22.09 (m, 2P);MS (m/z): 1337 [M+H]⁺.

Synthesis of G[5′]pppp[5′]C-18-Biotin (7b):

The coupling reaction of ImGMP with Bio-18-CTP TEA salt in the presenceof ZnCl2 provides the corresponding G[5′]pppp[5]C-18-Biotin (7b).

Compound 7a is also shown in FIG. 2, as the attachedbiotin-linker-nucleobase disclosed in the structure labeled Bio-18UTP.Each of the structures shown in FIG. 2 are examples of a non-cleavablelinker attached to a dinucleotide cap of the present invention.

Example 14 Synthesis of m₂ ^(7,3′O)G[5′]pppp[5′]U-Aminoallyl-18-Biotin(9)

To a stirred solution of aminoallyl UTP (0.08 g, 0.085 mmol) and m₂^(7,3′O)ImGMP (0.075 g, 0.17 mmol) in 5.0 mL dry DMF, ZnCl₂ (0.023 g,0.17 mmol) was added under nitrogen atmosphere and the reaction mixturewas stirred at room temperature for 6 hr. After 6 hr, the reactionmixture was added to a solution of EDTA disodium (0.13 g, 0.34 mmol) in100.0 mL of water at 0° C. The resulting aqueous solution was adjustedto pH 5.5 with glacial acetic acid and loaded on a DEAE Sephadex column.The desired product was eluted using a linear gradient of 0-1M TEAB, pH7.5 and the fractions containing the product were pooled, evaporated andconcentrated to 10.0 mL TEA salt of (9). The resulting 10.0 mL waspassed through a Strata-X-AW column and washed with 10.0 mL waterfollowed by 10.0 mL MeOH. Then, the desired compound was eluted with15.0 mL of NH₄OH/MeOH/H₂O (Feb. 25, 1973) and the collected solution wasevaporated and dried to give a fine white powder (9). (Yield: 0.034 g,41%).

Data for Compound (9): ¹H NMR (D₂O, 400 MHz) δ8.10 (s, 1H), 6.52 (d,J=16.0 Hz, 1H), 6.43 (m, 1H), 5.98 (d, J=3.6.0 Hz, 1H), 5.91 (d, J=6.0Hz, 1H), 4.46-4.15 (m, 12H), 4.12 (s, 3H), 3.72 (d, J=5.6 Hz, 2H), 3.49(s, 3H); ³¹P NMR (D₂O, 162 MHz) δ-10.27 (m, 2P), -21.79 (m, 2P); MS(m/z): 911 [M+2H]⁺.

Example 15

Scheme to Make Compounds 10, 11, and 12

The coupling reaction of m₂ ^(7,2′O)G[5′]pppp[5′]U-Aminoallyl,M^(7,2′F)G[5′]pppp[5′]U-Aminoallyl, or m⁷ 3′ dG[5′]pppp[5′]U-Aminoallylwith Biotin-XX-SE in the presence of sodium borate buffer affords thecorresponding compounds 10, 11, and 12, respectively.

Compounds 9-12 as illustrated have a non-cleavable linker. The structureillustrated in FIG. 1 can correspond to compounds 9 and 12 having fourphosphate molecules connecting the nucleobases of the dinucleotide capwith a cleavable linker as indicated by the presence of the disulfide(S—S) bond within the carbon chain of the biotin reporter moiety. Analternative synthesis scheme for compounds 9 and 12 is also shown inFIG. 4.

Example 16

Synthesis of m⁷G[5′]pppp[5′]U—SS-Biotin (13)

60 mg (0.067 mmol) of m⁷G[5′]pppp[5′]U-Aminoallyl (2) was dissolved in 5mL of 0.1 M sodium borate buffer (pH 8.5) and the solution was stirredfor 15 min at room temperature. Immediately before use, a solution of50.72 mg (0.101 mmol) of Biotin-SS—SE NHS ester in 2 mL of DMSO wasprepared. To a stirred solution of m⁷G[5′]pppp[5′]U-AA was addedBiotin-SS—SE NHS ester slowly during a period of 10 min The reaction wasallowed to take place for 4 hr at room temperature. After 4 hr, thereaction mixture was loaded onto an AMBERCHROM™ XT20 RP column andeluted with 2-50% acetonitrile to obtain pure m⁷G[5′]pppp[5′]U—SS-Biotin(13) in 83.62% yield (72 mg). The molecular weight of this compound asrevealed by MALDI-TOF was 1351.37 Da (Expected Exact Mass 1351.30 Da).

Compound 13 is depicted as having a cleavable linker as indicated by thepresence of a disulfide (S—S) bond in the carbon chain of the biotinmolecule. This compound is also depicted in FIG. 1 and in FIG. 4 whichillustrates a scheme for the synthesis of compounds 12, 13, and 14.

Example 17

Scheme to Make Compounds 14, 15, 16, and 17

The coupling reaction of m₂ ^(7,3′O)G[5′]pppp[5′]U-Aminoallyl or m₂^(7,2′O)G[5′]pppp[5′]U-Aminoallyl or m^(7,2′F)G[5′]pppp[5′]U-Aminoallylor m₂ ⁷3′dG[5′]pppp[5′]U-Aminoallyl with Biotin-SS—SE in the presence ofsodium borate buffer affords the corresponding compounds 14, 15, 16, and17, respectively.

Compounds 14 and 17 are depicted as having a cleavable linker asindicated by the presence of a disulfide (S—S) bond in the carbon chainof the biotin molecule. These compound are also depicted in FIG. 1 andin FIG. 4 which illustrates a scheme for the synthesis of compounds 14and 17.

Example 18

Scheme to Make Compounds 18-22

The coupling reaction of ImGMP with the modified C8-position (R₅) ofm⁷GDP or m⁷GTP also containing 2′ or 3′ modifications provides thecorresponding cleavable, biotinylated cap analog in the presence ofZnCl₂. Cap analog m^(7,8-S—S-Biotin)G[5′]pppp[5′]Nuc (18), Cap analog m₂^(7,3′O,8-S—S-Biotin)G[5′]pppp[5′]Nuc (19), Cap analog m₂^(7,2′O,8-S—S-Biotin)G[5′]pppp[5′]Nuc (20), Cap analog m₂^(7,2′F,8-S—S-Biotin)G[5′]pppp[5′]Nuc (21), and Cap analogm^(7,8-S—S-Biotin)3′dGG[5′]pppp[5′]Nuc (22).

Example 19

Scheme to Make Compounds 23-27

The coupling reaction of ImGMP with the corresponding substituted2-S—S-BiotinGTP at the modified NH₂-position (R₄) of m⁷GDP or m⁷GTP alsocontaining 2′ or 3′ modifications provides the corresponding cleavable,biotinylated cap analog in the presence of ZnCl₂ provides thecorresponding compounds 23, 24, 25, 26 and 27, respectively.

Example 20

Scheme to Make m^(7,2′-S—S-Biotin)G[5′]pppp[5′]Nuc, Compound 28

The coupling reaction of ImGMP with 2′ modified m^(7,2′-S—S-Bio)GTP inthe presence of ZnCl₂ provides the corresponding cap analog compound 28.

Example 21

Scheme to Make m^(7,3′-S—S-Biotin)G[5′]pppp[5′]Nuc, Compound 29

The coupling reaction of ImGMP with 3′ modified m^(7,3′-S—S-Bio)GTP inthe presence of ZnCl₂ provides the corresponding cap analog compound 29.

Example 22 Synthesis of Biotin-18-UTP TEA (31)

1.444 g (2.06 mmol) of Allylamine UTP (AA-UTP) (a) was dissolved in 40mL of 0.1 M sodium borate buffer (pH 8.5) and the solution was stirredfor 15 min at room temperature. Immediately before use, a solution of1.517 g (2.266 mmol) of Biotin XX-SE-NHS ester in 10 mL of DMSO wasprepared. To a stirred solution of AA-UTP was added Biotin XX-SE-NHSester slowly during a period of 20 min The reaction was allowed to takeplace for 4 hr at room temperature. After 4 hr, the reaction mixture wasloaded onto a DEAE Sepharose column and eluted with 1-100%triethylammonium bicarbonate buffer (pH 7.5, 4° C.) to obtain pureBio-18-UTP TEA (31). The molecular weight of this compound as revealedby MALDI is 992.01Da (Expected Exact Mass 992.26 Da). The structure of(31) is shown in FIG. 2.

Data for Compound 31: ¹H NMR (D₂O, 400 MHz) δ8.97 (s, 1H), 6.45 (m, 1H)6.32 (d, J=16.4 Hz, 1H), 6.00 (d, J=5.2 Hz, 1H), 4.61 (m, 1H), 4.50-4.42(m, 3H), 4.32-4.22 (m, 3H), 3.92 (m, 2H), 3.31 (m, 1H), 3.17 (t, J=6.8Hz, 4H), 2.98 (dd, J=13.2, 5.2 Hz, 1H), 2.77 (d, J=12.8 Hz, 1H),2.34-2.20 (m, 6H), 1.74-1.25 (m, 18H); ³¹P NMR (D₂O, 162 MHz) δ-7.27 (d,J=19.9 Hz, 1P), -10.39 (d, J=20.6 Hz, 1P), -21.23 (t, J=19.8 Hz, 1P); MS(m/z): 992 [M+H]⁺.

Example 23 Scheme to Isolate Capped RNA

Cap analogs containing a reporter moiety allow for isolation andpurification of only the capped RNA following transcription. Suchisolation methods are readily known to one of skill in the art. FIG. 5-8illustrate schemes for the isolation of purified capped mRNA havingbiotin as the reporter moiety. The capped mRNA is captured by usingstreptavidin-coated magnetic beads which act as a solid matrix and havea high affinity for biotin. Uncapped RNA will not be bound by the solidmatrix and will be subsequently washed out. The bound, capped mRNA willbe dissociated from the reporter moiety attached to the solid matrix byusing either a 50 mM DTT or 100 mM β mercaptoethanol solution and thenrecovered and purified by using a spin column. The resulting capped RNAis ready for transfection and translation experiments and assays. Thiskind of technology is applicable for universal labeling and detaching,and has important applications in vaccine production as well as animportant impact in the field of therapeutics.

Also envisioned is a kit containing a biotinylated cap analog. A userwould synthesize an RNA transcript with at least one biotin reportermoiety or attach the biotin reporter moiety post-translation andsubsequently isolate the capped RNA. The cap would be attached to the 5′end of the mRNA transcript. The kit would also comprisestreptavidin-coated beads (possibly magnetic) and free biotin to elutethe RNA from the streptavidin as shown in FIG. 5-8. The resultingisolated RNA could be used in experiments to identify proteins and RNAthat bind to it. Protein analysis can be performed on a massspectrometer instrument, as would be understood by the skilled artisan.

Once the 5′ biotinylated-labeled RNA is isolated it can be used for pulldown experiments to study RNA-protein interactions. First, thebiotinylated RNA will be subjected to binding of protein. The bindingbetween 5′ biotinylated RNA and Rat Brain lysate (protein source) can beinduced by incubation in a binding buffer (20 mmol Tris, 1 M NaCl, 1 mMEDTA, 0.02% Triton X-100, pH 8.0) for 10 min with either unmodifiednon-full length (NFL) 3′ UTR (−) or biotinylated cap NFL 3′ UTR. Afterbinding, the NFL 3′ UTR ribonuclease phosphate (RNP) complexes werepulled down with Globin Clear Streptavidin beads (100 μL per sample).The pull down of the RNP complexes will be analyzed by Western blots.(A. Lal et al. The EMBO Journal 23, 3092-3102, (2004); R. Pullmann, Jr.et al. The Journal of Biological Chemist, 281(33), 23456-23463, (2006)).

Example 24 Disulfide Bond Cleavage

The disulfide bond (S—S) can be cleaved under mild reducing conditionswith agents such as 50 mmol dithiothreitol (DTT) orTris(2-carboxyethyl)phosphine hydrochloride, (TCEP) or 100 mmol2-Mercaptoethanol, and or 1% Sodium borohydride (Shimkus, M., et al.(1985). Proc. Natl. Acad. Sci. USA 82, 2593-2597; Dawson, B. A., et al.(1989). J. Biol. Chem. 264(22), 12830-12837; Kirkley, T. L., Anal.Biochem, 180, 231-236 (1989); Andrews, P. C., Dixon, J. E., Anal.Biochem, 161, 524-528 (1987); Schonberg, A., Chem. Ber., 163-164 (1935);Rauhut, M., et. al., JACS, 81, 1103-1107 (1959).

Schemes for the isolation of capped RNA and cleavage of the reportermoiety at the disulfide bond are illustrated in FIG. 5-8. The presenceof the linker, aminoallyl, on the dinucleotide cap compound facilitatesthe attachment of the reporter moiety, biotin, as the example in FIG.5-8, to the dinucleotide cap.

Example 25 T7 RNA Transcription

T7 RNA polymerase transcription was performed by using mMessagemMachine® T7 kit (Ambion) in 20 μL final volume, and contains thefollowing reagents at the final concentrations indicated: 1 μglinearized AmbLuc PolyA DNA, 1× reaction buffer, 7.5 mmol of each ATP,UTP, and CTP, 1.5 mmol GTP, 6.5 mmol of mCAP and 2′ fluoro cap analogs,and 50 U/μL of T7 RNA polymerase. The transcription reactions wereincubated at 37° C. for 2 hours. In order to hydrolyze the remainingplasmid DNA, 1 μL of turbo DNAse was added to the reaction mixture, andfurther incubated at 37° C. for 15 minutes. The transcribed capped anduncapped mRNAs were purified by using the MEGAclear™ Kit (Ambion).

FIGS. 10 and 11 show the results of selected reporter moiety labeled capanalogs as evaluated in an AmbLuc Poly(A) (Ambion) in vitrotranscription assay. The cap analogs transcription yields werecomparable for modified and standard cap analogs. As shown in FIG. 11,analysis of each transcribed mRNA indicates that all the mRNAs are notdegraded and retain great integrity. Assays were performed on an Agilent2100 Bioanalyzer.

In some embodiments, the cap analog is used for the synthesis of 5′capped RNA molecules in transcription reactions. Substitution of the capanalog for a portion of the GTP in a transcription reaction results inthe incorporation of the cap structure into a corresponding fraction ofthe transcripts. Capped mRNAs are generally translated more efficientlyin reticulocyte lysate and wheat germ in vitro translation systems. Ithas been found that in vitro transcripts should be capped formicroinjection experiments because uncapped mRNAs are rapidly degraded.Cap analogs are also used as a highly specific inhibitor of theinitiation step of protein synthesis.

Example 26 Gel Shift Assay

A Gel Shift assay was performed by using the MAXIscript™ kit (Ambion,Inc.) following the manufacturer's protocol. The assay determines if themodified cap analogs were substrates for T7 RNA polymerase. Typical 20μL of T7 RNA polymerase transcriptions contained the following reagentsat the final concentrations indicated: linearized pTri β actin vectortemplate, 0.5 μg; ATP, 2 mmol; GTP, 0.4 mmol; 1.6 mmol each CTP and UTP,in a separate reaction; 10× reaction buffer, 4×; T7 RNA polymerase, 50units/μL; (α-³²P) ATP, 800 (Ci/mmol); and DEPC water. The controlreaction was a normal in vitro transcription reaction, in which no capanalog was added. The transcription reactions were incubated at 37° C.for 2 hr, after which the reaction mixtures were then applied to a 20%dPAGE gel. The assay detects specific structure or size changesdescribed as gel shifts. When structure change or size change occurs itcreates complexes that migrate slower during gel electrophoresis thanthe original complex. As shown in FIG. 9, modified cap compounds werefound to be substrates for T7 RNA polymerase, as determined by gel shiftassays that clearly revealed that capped RNAs were formed, based onslower migration relative to uncapped RNAs. The new capG[5′]pppp[5′]U-AA analogs comprised about 65% of capped RNA.

Although the present disclosure is described with respect to variousembodiments and examples, various modifications may be made withoutdeparting from the spirit and scope of the invention.

1. A composition comprising:

wherein, B is a nucleobase; R₁ is selected from a halogen, OH, and OCH₃;R₂ is selected from H, OH, and OCH₃; R₃ is CH₃ or void; R₄ is NH₂; R₅ isH; and n is 1, 2 or 3; and wherein, a linker is attached to one of R₁,R₂, R₄, R₅, or B.
 2. The composition as recited in claim 1, wherein saidlinker is selected from N, S, and O.
 3. The composition as recited inclaim 2, wherein said linker is selected from an aminoallyl([—CH₂]—CH₂NH₂) where n=2−18, a secondary amine and an alkyl (C₃-C₁₀)NH₂chain.
 4. The composition as recited in claim 2, further comprising areporter moiety attached to said linker.
 5. The composition as recitedin claim 4, wherein said reporter moiety is selected from an affinitytag and an epitope tag.
 6. The composition as recited in claim 5,wherein said affinity tag is selected from biotin, iminobiotin, avidin,and streptavidin.
 7. The composition as recited in claim 6, wherein saidbiotin is selected from C₅-C₂₀-biotin, SS-biotin, XX-biotin, and NHSester compounds thereof.
 8. The composition as recited in claim 1attached to a 5′ end of an RNA molecule.
 9. The composition as recitedin claim 3 attached to the 5′ end of an RNA molecule.
 10. Thecomposition as recited in claim 4 attached to the 5′ end of an RNAmolecule, forming a reporter moiety/RNA molecule complex.
 11. Thecomposition as recited in claim 7 attached to the 5′ end of an RNAmolecule.
 12. The composition as recited in claim 1, wherein R₃ is void,the nucleobase is selected from the group consisting of a pyrimidine, apyrimidine nucleobase analog, a purine, a purine nucleobase analog, andnatural, synthetic and derivative nucleobases thereof, a) a linker isattached to one of the pyrimidine or purine nucleobases, and b) areporter moiety is attached to the linker.
 13. The composition asrecited in claim 12, wherein said reporter moiety is an affinity tagselected from biotin, iminobiotin, avidin, and streptavidin.
 14. Thecomposition as recited in claim 12 attached to the 5′ end of an RNAmolecule.
 15. The composition as recited in claim 1, wherein R₃ is CH₃,the nucleobase is selected from the group consisting of a pyrimidine, apyrimidine nucleobase analog, a purine, a purine nucleobase analog, andnatural, synthetic and derivative nucleobases thereof, a) a linker isattached to one of the pyrimidine or purine nucleobases, and b) areporter moiety is attached to the linker.
 16. The composition asrecited in claim 15, wherein said reporter moiety is an affinity tagselected from biotin, iminobiotin, avidin, and streptavidin.
 17. Thecomposition as recited in claim 15 attached to the 5′ end of an RNAmolecule.
 18. The composition as recited in claim 1, wherein R₃ is CH₃,the nucleobase is selected from the group consisting of a pyrimidine, apyrimidine nucleobase analog, a purine, a purine nucleobase analog, andnatural, synthetic and derivative nucleobases thereof, a) a linker isattached to one of R₁, R₂, R₄, or R₅, and b) a reporter moiety isattached to the linker.
 19. The composition as recited in claim 18,wherein said reporter moiety is an affinity tag selected from biotin,iminobiotin, avidin, and streptavidin.
 20. The composition as recited inclaim 18 attached to the 5′ end of an RNA molecule.
 21. A method ofsynthesizing a dinucleotide cap analog comprising: a) providing aguanosine nucleoside comprising either a 2′ substituent or a 3′substituent and optionally comprising a linker; b) phosphorylating thenucleoside, forming a nucleotide; c) methylating the nucleotide; d)adding a phosphorylated second nucleotide optionally comprising alinker; e) coupling said first nucleotide with said second nucleotide,forming a dinucleotide cap analog.
 22. A method for isolating adinucleotide capped molecule comprising: a) providing a nucleic acidmixture containing the composition as recited in claim 10; b) bindingthe reporter moiety of step a) to a substrate; c) extracting the complexof step b) from the nucleic acid mixture; d) removing the linker fromthe capped nucleic acid; and wherein capped nucleic acids are isolated.23. A composition comprising: an antigen presenting cell transfectedwith the composition of claim
 1. 24. A kit for capping an RNA transcriptcomprising a cap analog having the structure:

wherein, B is a nucleobase; R₁ is selected from a halogen, OH, and OCH₃;R₂ is selected from OH, OCH₃, and H; R₃ is CH₃ or void; R₄ is NH₂; R₅ isH; and n is 1, 2 or 3; and wherein, a linker is attached to one of R₁,R₂, R₄, R₅, or B; a reporter moiety is attached to the linker; at leastR₁, or R₂ is OH; and b) an RNA polymerase.
 25. A cell comprising an RNAmolecule wherein the composition of claim 1 is attached to the RNAmolecule.